repowering a sailboat

Repowering a Boat: What You Should Know

Does your boat engine need to be replaced? If so, you should review the pros, cons, costs, and considerations for repowering a boat. Stay tuned to discover everything you need to know! 

What Does Repowering a Boat Entail?

So, what does repowering a boat mean? This term refers to replacing your old boat engine with a newer alternative. Doing so makes your vessel faster, more efficient, and less likely to break down. 

Pros of Repowering a Boat

As mentioned, repowering your boat helps it run faster and more efficiently. In addition, here are some of the benefits:

1. Improve Performance

Replacing your old engine with a new one is a phenomenal way to maximize your boat’s overall performance. Generally, repowering a boat improves the power-to-weight ratio (making your boat easier to handle), maximizes speed and power, and offers a more enjoyable boating experience overall. 

2. Extend the Boat’s Lifespan

 A properly-maintained boat engine lasts many years – extending your time on the water. And not only do newer engines feature advanced technology and higher-quality parts, but they allow for longer service intervals. That means they require less maintenance.

Read Next: Boat Maintenance Guide

3. Increase Resale Value

Thinking about selling your boat? (Either sooner or later?) Because the value of your boat increases when you replace your old engine with a newer, more powerful one. Generally, buyers are more interested in purchasing modern, efficient, and dependable vessels. 

4. Improve Fuel Economy

We probably don’t need to remind you that gas prices are increasing. However, newer engines allow you to spend less money on gas or fuel .

5. Better for the Environment

When repowering your boat, you can upgrade to an engine that uses less fuel and meets the current carbon pollution rules. Manufacturers make the newest machines to be as green as possible . And by reducing pollution, your boat becomes safer for the environment and the seas.  

Read Next: Responsible Boating Guide

Cons of Boat Repowering

Naturally, there are two sides to every coin. Here are some drawbacks of repowering: 

1. Boat Downtime Needed

Depending on the vessel’s size and the work’s complexity, the repowering process takes some time (several days or weeks.) Because you can’t operate your boat during that time, you must plan your schedule accordingly. 

2. Compatibility

Believe it or not, certain engines aren’t compatible with certain types of boats. Therefore, you must verify that your fuel and exhaust systems, buttons, gauges, and electrical links work with the new engine. And note that the price might increase depending on any necessary changes. 

3. Installation

Usually, you’ll need to hire professional marine technicians to handle a project of this size. They can verify that everything was done correctly and that the installation is successful. However, their expertise comes with a price, and hiring experts bumps the overall cost. 

4. Repowering Costs

So, how much does it cost to repower a boat? Typically, upgrading your boat’s power source costs several thousand dollars. However, your exact price depends on factors like boat size, engine type, installation fees, boat modifications, and additional equipment.

Our advice? Do your research and collect quotes from multiple sources. That way, you can thoroughly assess your options and select the one that works best for you. 

What to Consider:

Decided that it’s time to repower your boat? Before you do, there are a few considerations to keep in mind: 

• Maintenance : There’s no getting around it – new engines require ongoing maintenance! When factoring this into your decision, consider the proximity of repair shops, what the warranty includes, and how easy it is to reach customer service. 
• R egulations and emissions standards:  Every boater must adhere to the local regulations and emissions standards. To avoid legal problems, your new engine must comply with laws regarding engine pollution, noise levels, and environmental concerns. 
• Compatibility:  It’s important to remember that certain engine types aren’t compatible with certain boat models. And just because someone suggests an engine model doesn’t mean it will automatically work for you. 

The Bottom Line

The benefits far outweigh the cost of repowering your boat. And if you’ve decided to upgrade your boat’s power system, we hope this guide answers your questions. 

On the Discover Boating Blog, you'll find boating advice, maintenance guides, and buying tips for both seasoned pros and first-time boaters. If you’re interested in learning how to care for your new boat engine, how to choose the right marine fuel and oil, or about the life expectancy of your boat engine , head to the Articles & Inspiration section of our website. 

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Repowering, Part 1 – The Decisions

Posted by Don Launer | Engine , Projects

New engine or rebuild? And should you install it yourself?

On a cold February day, Don studies his engine replacement information. Delphinus rests outside awaiting her new engine.

Chances are your boat is like a member of the family. You could no more dispose of it than sell your only child. But, inevitably, the day arrives when you realize that your power plant is on its last legs, and there are some important decisions to be made.

Some boatowners go to the boatyard, write a check, and say effortlessly, “Call me when it’s ready.” For most of us, however, it’s a traumatic moment. After all, repowering an inboard auxiliary sailboat is a lot more involved than simply dropping a new outboard onto the transom.

For diesel engines, the symptoms begin to develop years before things become critical. Whereas your brand-new diesel would start within the first turn, now the cranking takes longer — and, if the weather is cold, much longer.

When Rudolf Diesel first patented his engine in 1892, it was a revolutionary idea. His engine used the principle of auto-ignition of the fuel. This idea, based on the work of English scientist Robert Boyle (1627-91), was that you could ignite the fuel from the heat produced by compressing the air in the cylinder. If this compression were great enough, the temperature in the cylinder could be raised enough to ignite the fuel-and-air mixture. In modern diesel engines, this compression ratio is between 14:1 and 25:1, which raises the temperature of the air in the cylinder to well above the burning point of the diesel oil that is injected into the cylinder (about 1,000 degrees F).

Compression, then, is the key to a successfully operating diesel. But when a diesel is up in years, cylinder walls and piston rings are worn and fouled with deposits, so they no longer make a good seal. Valves and valve-seats have also become pitted and fouled and don’t seal properly. Thus, it becomes much more difficult to get the compression necessary for ignition, especially when the engine block is very cold and rapidly saps away the heat of compression.

Biting the bullet

Discussing the proposed engine replacement with Tom Dittamo of Harbor Marine Engines.

When the day finally arrives for you to bite the bullet, there are two options: get the engine rebuilt or buy a new one. If the horsepower of the old engine was perfect, if it pushed you through heavy winds and waves when they were right on the nose, and if that engine has always been freshwater-cooled and has not had other serious problems, rebuilding that old engine might be more compelling. Certainly it would be less expensive.

But if your present engine is very old and has had raw saltwater cooling, chances are that having it rebuilt will not be practical. There will be rust, frozen bolts, parts to replace, and probably great difficulty in getting those parts. Even though the cost of rebuilding an old engine is typically about half that of a new engine, you may very well be throwing money away on a rebuilding venture. And if you have always felt that you could use just a few more horsepower to get you through those nasty conditions, now is a good time to upgrade.

Remember that when you decide to go with a new engine there are many more costs involved than just the price of the engine itself. Engines today, which provide the same horsepower as your old engine, are usually lighter and smaller and rotate at higher speeds.

These smaller dimensions in width, height, and length make it almost certain that your engine bed will have to be rebuilt to accommodate the smaller engine, since its mounts will probably be closer together.

It’s also important to know the type of transmission on your new engine. Basically, there are three different types:

• Parallel is a transmission whose propeller-shaft coupler is in line with, or parallel to, the engine’s crankshaft.
• Angle-Drive is a transmission whose coupler is at a downward angle to the crankshaft.
• V-Drive is a version in which the transmission is forward of the engine and makes a V-turn to drive a propeller shaft leading aft.

The new Yanmar 3GM30F is delivered early, which gives Don adequate time in which to measure it and familiarize himself with it.

Each of these configurations presents its own problems when rebuilding the engine bed. The smaller fore-and-aft dimensions will probably also mean that you’ll need a new and longer prop shaft unless you can set the new engine farther aft on the beds. Having a new shaft is probably a good idea anyway. After the old engine has been removed and the old shaft has been slid out of its stuffing box, you’ll probably see rings of wear in the shaft where the stuffing box (and sediment) have created grooves. If your old shaft is more than a decade old, you’ll probably find that the flange coupling is so frozen onto the shaft with rust that it’s impossible to free it without further ruining the shaft.

Also, if you didn’t previously have a flexible coupling or Drivesaver, now is a good time to add this item, which will help protect your new transmission in the event of the propeller picking up a piece of wood or a heavy line. If you’re already using a flexible coupling between the engine and the shaft, chances are that the bolt holes in this flexible coupling or Drivesaver will not match your new engine’s coupler, and a new, matching, flexible coupling will have to be purchased.

As for the propeller, there’s a 50-50 chance that the new engine may rotate in the opposite direction from the old engine. (If your present engine turns the prop shaft counterclockwise in forward gear, as seen from the stern, you now have a left-hand prop. If the new engine has a clockwise rotation, you need a new prop.)

Even if the direction of rotation of the new and old engines is the same, chances are that the engine speed, the horsepower, and the transmission gear ratio of the new engine will be different from the old. This will probably mean a new propeller of different pitch, diameter, or number of blades, making your old prop obsolete.

Free consultation

Before and after: preparations for the installation of a smaller Beta Marine engine in a C&C 30 required a new engine bed and oil drip pan to be constructed. This boat began life with an Atomic 4 which was later replaced by a Bukh and finally the Beta.

Most engine installation manuals give charts showing the recommended prop for your particular displacement and hull configuration, and most propeller manufacturers provide a free consultation service to determine the type of new prop you’ll need when repowering. Michigan Propellers, for instance, has a Pleasure Boat Prop-it-Right Analysis Form, which will suggest the correct propeller for your new engine.

On some boats, the engine and propeller shaft are deliberately installed at a slight angle off the fore-and-aft centerline of the boat. This may have been done to offset the tendency of a single engine to push the stern to one side or the other or to allow the shaft and prop to be removed without removing the rudder. If your boat has an offset driveshaft, repowering with an engine whose shaft rotates in the same direction as the old engine may be preferable. ( We have an offset shaft on our C&C 30. We repowered with opposite rotation and are satisfied with the outcome. It seems like this should have mattered more than it did. —Ed. )

The smaller proportions of a new engine and the rebuilding of the engine bed will also mean that your present oil drip pan beneath the engine will no longer fit, and a new pan will have to be fabricated and installed.

There is one complication of a physically smaller engine that may be overlooked. If you’ll be using your engine to supply hot water through a heat exchanger, the water connections on the new engine might well be lower than on the previous engine. If the heat-exchanger water lines from the engine to the hot water tank slope upward, an air-lock can develop in the heat-exchanger coil in the hot water tank that will prevent water flow and, consequently, heat exchange. One way to overcome this problem is by installing an expansion tank at the highest point in the water lines at the hot water tank. The pressure cap on this tank should match that of the one on the engine, and filling the water system can be done through the filler cap of the new tank.

Fuel-return line

With diesel engines there’s another thing to consider. Some diesels had just one fuel line going from the tank to the engine. Most modern diesels, however, also require a fuel-return line from the engine to the tank (often called the overflow fuel line). Depending on an engine’s design, the amount of fuel returned to the tank via this line can vary greatly.

If you had an engine with a single fuel line, the chances are that you don’t have a fitting on top of the fuel tank(s) for this new fuel-return line. This problem can usually be solved by removing the current air-vent fitting at the top of the fuel tank and substituting a T-fitting. One side of this T can then still be used for the air vent while the other side can be used for the fuel-return line. This problem also will be encountered when changing from a gasoline engine to diesel.

It’s also likely that with a new engine, the water, fuel, and exhaust systems may have to be rebuilt or re-sized. Even if this isn’t the case, when the old engine is removed is a good time to replace those old hoses.

If you are considering selling your boat within the next few years, it might be tempting to believe the value will increase enough to offset the money you have put into a new engine and its installation. But although a boat will be worth more with a new engine, the increase in value will probably not equal your investment when you sell your boat. The same caveat is true if you convert from gas to diesel. But here we are discussing repowering your boat because you want to use it for many more years, not with the idea of selling it.

Do it yourself?

Most owners will hand over the repowering project to a knowledgeable, qualified, and reputable installer. Still, it’s valuable to know the potential problems along the way. If you have decided to have the job done professionally, there are several preliminary steps to take:

• Only accept bids from installers who have actually examined your boat.
• Consider the reputation of the installer and the yard.
• Ask whether they have installed this type of engine before.
• Ask for references from owners of boats similar to yours who have had the same job done.
• Make sure that all associated work is specified on the proposal.
• Be sure that the final installation will conform to American Boat and Yacht Council (ABYC) standards.

Some boatowners will want to tackle the job themselves. If you do your own installation, there are much greater benefits than saving money. You will end up with an intimate knowledge of your new installation. This, alone, is a great incentive.

If you decide to do the job yourself, it’s still a good idea to have a professional in your corner, someone who is a dealer for your new engine or who has done engine installations, and whom you can trust, talk to, and order parts from. If you’re doing your own work, the closer the yard is to your home, the better. And if you don’t want to tackle the whole job yourself, you may elect to do just the engine rewiring, the exhaust system, the water system, or the fuel system, after the new engine has been installed on its bed and aligned.

Whether you do it yourself or have the engine installed by a professional, the job requires engineering judgment and good mechanical skills.

We were fortunate that for years there was an engine mechanic near us who would give us excellent and detailed advice whenever we had a do-it-yourself engine job to tackle. Tom Dittamo, owner of Harbor Marine Engines, in Lanoka Harbor, N.J., has his business in a marina less than 15 minutes from our home. Tom is also a Yanmar dealer, so we chose that yard, Laurel Harbor Marina, in Lanoka Harbor, for our haulout and engine replacement.

We bought our new engine from Tom six months before beginning our project. He stored it in his shop at the marina during this time, which allowed me to go in for all the necessary measurements whenever I needed to. This enabled us to plan well ahead for our project and purchase all the ancillary gear necessary. (This early engine purchase, which was suggested by Tom, also saved us 5 percent on the manufacturer’s price increase that went into effect shortly after we ordered the engine).

Start early

Replacing an engine often means replacing the propeller as well. The C&C 30 gets a new right-hand Michigan Wheel 15 x 9 2-blade propeller. Later this was replaced by an Autoprop.

Changing inboard engines is not a simple project. If you are very adept at major projects, if you are a good mechanic, if you have lots of time and patience, and most of all if you enjoy working on boats and this type of challenge, then you should start doing your homework and putting together a loose-leaf notebook.

Begin buying the necessary parts months in advance. I started buying my conversion gear six months before the start of my project, and that was not too soon. I discovered that the delivery of a new prop would take six weeks and the longer prop shaft would take almost as long, even though it was always: “I’ll have it for you next week.”

It’s important to learn as much about your new engine as possible before you start the project. There are many engine distributors who offer one- or two-day seminars specifically targeted at owners of auxiliary engines. Mack Boring & Parts Company, which sells Yanmar engines and parts, has one- and two-day owner seminars on Yanmar engines that are invaluable. These classes are given at Mack Boring locations in Union, N.J., Wilmington, N.C., Middleborough, Mass., and Buffalo Grove, Ill. The classes cover the theory of operation, explain all the parts of your new engine, cover routine maintenance, and include a hands-on session that gives participants the opportunity to do routine maintenance on the engine they will actually own, including adjusting and bleeding it.

Incidentally, one item that is invaluable in setting up the placement of a new engine on the rebuilt bed is an engine jig, which can usually be rented from the engine distributor. The jig consists of light-weight metal framework that locates the proper position of the engine mounts and shaft alignment. It copies the exact size and angle of the real engine and can be aligned with the prop-shaft coupling, revealing whether there has to be any change made in the engine bed or mounts long before the engine is swung into position.

The alternative to the engine jig uses another type of alignment method that will be discussed further in Part 2 of this series, which will run in the November/December issue of Good Old Boat .

Installation manuals

Nearly all engine manufacturers have comprehensive installation manuals that are essential for the do-it-yourselfer. These manuals, which should be part of your repowering notebook, have step-by-step installation instructions, including alignment procedure; wiring diagrams; engine specifications, dimensions, shaft and prop recommendations; and fuel, water, and exhaust-hose requirements. It’s also a good idea to purchase a service manual for your engine. It will be a handy reference for the future, and it gives some installation information that isn’t necessarily shown in the installation manual.

New engines come with their own instrument panels. If you have an instrument panel recess in your cockpit, especially one that is molded into a fiberglass boat, make sure that the new engine’s instrument panel will fit into the old recess. If it won’t, it might be tempting to try to use the old panel with the new engine, but this usually is asking for a lot of headaches, including replacing the tachometer, oil and temperature gauges, and wiring. Some manufacturers have several panel options of different sizes. Yanmar, in their GM series for auxiliaries, have three control panels of varying sizes and options.

Repowering a boat from a gasoline engine to diesel power needs extra consideration. Diesel engines of equivalent horsepower are usually physically larger than their gasoline counterparts. You may find, however, that the Atomic 4 in your boat has much more horsepower than the diesel you will replace it with. Many smaller boats were powered with an A4 and a direct-drive transmission. Only half the engine speed range, and thus roughly half the horsepower, was used. These direct-drive boats were equipped with very small props.

Bed modification

Out with the old (Volvo)

Even if you’re sure an appropriate diesel will fit in the engine compartment, you’ll probably need to rebuild or modify the engine bed. Consider the maximum-diameter prop that can be fitted to your boat and still have the required tip clearance. Match this against the prop that the new engine will need. Not all gasoline tanks and fuel lines are compatible with diesel fuel and, as mentioned previously, a fuel-return line will also have to be added. The primary water-separator/ fuel filter will also need to be replaced. In some cases, the prop shaft may have to be increased in size which, in turn, means a new stuffing box.

In with the new (Yanmar)

Most of us have a pretty good idea how much power we need, based on the performance of our previous engine. The old rule-of-thumb for auxiliaries of 2 hp for every 1,000 pounds of displacement is usually pretty good. If you really want to get into the calculations, then consult Dave Gerr’s Propeller Handbook or Francis Kinney’s Skene’s Elements of Yacht Design. Another source of information is at http://www.boat diesel.com on the web. This site, which provides a wealth of information on diesels, charges a $25 membership fee. If you click on Propeller/Power/ Shaft Calculations, you can find the proper shaft size, the power required for a given hull, and the recommended propeller specifications.

Be sure to check the alternator options available for your new engine. If your electrical consumption is high, as is the case with a refrigeration system or a watermaker, be sure to specify the appropriate alternator when you order the new power plant.

Engines for an auxiliary must, above all else, be reliable. When selecting the manufacturer of your new engine, do your homework. Talk to other sailors who have had an engine replacement recently and get their opinions. Get information from various engine companies and local marine mechanics, check out these engines at boat shows, and talk to the manufacturers’ reps.

When you’re finally back in the water with a new engine, you’ll feel much more inclined to take that long cruise you’ve been delaying for years, safe in the knowledge that you have a new power plant of high reliability for which parts are readily available.

Article taken from Good Old Boat magazine: Volume 5, Number 5, September/October 2002.

Part 2 of Don’s repowering series , with a focus on installation, will appear in the November/December 2002 issue of Good Old Boat .

Back To Top

American Boat and Yacht Council (ABYC) 410-956-1050 http://www.abycinc.org

Beta Marine 252-249-2473 http://www.betamarinenc.com

BoatDiesel http://www.boatdiesel.com

Harbor Marine Engines Laurel Harbor Marina 609-971-5797

Mack Boring 908-964-0700 http://www.mackboring.com

Michigan Wheel Corporation 616-452-6941 http://www.miwheel.com

Perkins-Sabre 253-854-0505 http://www.perkins-sabre.com

Vetus 410-712-0740 http://www.vetus.com

Volvo Penta of the Americas Inc. 757-436-2800 http://www.penta.volvo.se

Westerbeke Corporation / Universal 508-823-7677 http://www.westerbeke.com

Yanmar America Corp. 847-541-1900 http://www.yanmar.com

Propeller Handbook , by Dave Gerr Ask BookMark 763-420-8923 Good Old Boat Bookshelf

Part 2 of repowering article

About The Author

Don lives on a waterway off Barnegat Bay, on the New Jersey coast. He keeps his schooner, Delphinus, at dockside next to his home. Although Barnegat Bay and the adjacent waterways frequently freeze solid, his boat has wintered in unfrozen water for the past 21 years, protected by a water-agitation system and an electric engine-compartment heater.

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Sailboat Engine Replacement Options

• By Ed Sherman
• Updated: June 16, 2020

It’s the end of another sailing season, and as you haul the boat and begin its winter layup, you have reminders aplenty that the 30-year-old auxiliary engine is getting tired. The intermittent no-start condition, oil and coolant leaks, and excessive smelly exhaust smoke are finally getting to you. As you prepare to change the oil and run some antifreeze through the block, it occurs to you that it might be time for an upgrade. What should you consider? What are your choices? What are the pitfalls? Follow along and we’ll set you straight.

First off, if your sailboat’s auxiliary engine is truly approaching its third decade (or older), you need to understand that there may be significant components besides the engine that are probably going to need replacement. Things like the exhaust system, primary engine wiring harness, instrumentation, engine- and transmission-control cables, fuel tanks, transmission, shaft, cutlass bearing and prop are all suspect and need to be carefully evaluated. When looking at your options, be sure to factor all these additional items into your budget projection. Your new engine is just a part of the big picture.

Need More Power?

Back in the 1970s and ’80s, a lot of new sailboats were produced with engines that, frankly, were a bit underpowered. I know; I owned one. It was fine until I hit a head-on current in a narrow channel; I clearly remember moving along at a half-knot under full power. This scenario repeated itself all too frequently in some of the other New England waters I cruised regularly. More get-up-and-go would have been greatly appreciated.

So if you’ve experienced similar frustration, now is the time to consider more horsepower. How much is enough? You’ll need to do a bit of research to determine the best possible choice.

Consider that a sailboat is just like an airplane that stays at sea level. Power-to-weight ratios do matter: The heavier the plane’s engines, the more thrust it needs to gain altitude. The whole idea is to find the ideal balance. Simply replacing your 25- or 30-horsepower auxiliary engine with a 75-horsepower turbocharged model might sound good, but there’s more to consider than pure muscle.

First off, the 75-horsepower engine might simply be too heavy for your boat. Next, since most cruising sailboats have displacement hulls, things like waterline length and actual weight count considerably, just as they do for airplanes. With a full-displacement hull form, you can squeeze only so much speed out of that waterline length. Adding more horsepower represents a significant economic waste.

RELATED: Monthly Maintenance: Getting Back Aboard

Besides weight, physical dimensions are of paramount importance. Is it possible to get a motor-mount configuration that will work with your choice of marine diesel engine and the existing engine bed in the boat? What about service-point access? The water-pump impeller might appear to be easily replaceable on your new engine when you look at it at the boat show, but what about when it’s been bolted into place? There’s nothing worse than an engine part you simply can’t reach when you need to in a hurry. And will your engine-room space require additional modifications to fit a new muffler, filter location, shaft coupler, etc.?

Remember that marine diesel engines require a considerable amount of fresh air to run properly. Especially if you plan to increase horsepower, you may need to add engine-room ventilation to keep that new power plant from suffocating.

Common-Rail Marine Diesel Engines

In recent years here in the States, officials at the Environmental Protection Agency, along with their counter­parts in Europe, have been working hard to create regulations that do two things: clean up diesel fuel by reducing sulfur content significantly, and eliminate emissions from the diesel combustion process.

EPA mandates now require what are described as “Tier 3” emissions standards for boats sold in the U.S., regardless of where they are made. The effect of this became evident this past fall, when I was one of the judges for Cruising World ’s Boat of the Year competition. Of the 24 boats we tested and compared, half were equipped with electronically controlled “common-rail” super-high-pressure fuel-­injection systems. The new diesels use a common chamber that is often, but not always, integrated into the engine’s cylinder head, and which holds fuel for all the cylinders in the engine. The fuel is pressurized by a pump that operates at much higher pounds-per-square-inch than those used in older systems, which sent fuel from the fuel pump directly to individual fuel injectors at each cylinder.

In older marine diesel engines, fuel pressure typically ranged from a low of about 1,500 psi to close to 4,000 psi. In these systems, the injectors opened when fuel was compressed to what is referred to as the injector “pop” pressure.

In common-rail diesel engines, injectors are still used, but the pressure in the rail chamber is on the order of 15,000 psi to 20,000 psi. Injectors, meanwhile, are controlled by electronic solenoid valves, whose opening and closing time is controlled by an onboard CPU that adjusts the duration of each burst of fuel based on data inputs like temperature, engine load and rpm.

Here’s the good news: You’ll never have to bleed air out of these systems, as they are completely self-bleeding. With older marine diesels, bleeding was a fairly common task required after fuel-filter changes or running out of fuel. This problem is simply eliminated with the common rail. All that’s needed is to crank the engine, and the high-pressure pump will take care of the rest. Now here’s the bad news: The biggest fear with these engines is a problem with the onboard electronics. Rather than carrying spare fuel injectors, long-distance cruisers may now want to carry spare injectors and a spare engine-control CPU.

The hope, of course, is that the reliability of the engines will negate the need for fuel-system maintenance; routine fuel- and oil-filter changes can still be done by the owner. Problems will arise, though, when an engine doesn’t perform as it should. These are complex machines, and without the proper skills and equipment (diagnostic computers and the ability to read error codes), a boat owner probably won’t find a way to sort things out as he might have with a traditional marine diesel.

The Kiwi delivery skipper was aboard one of the boats I boarded during the boat show in Annapolis. It was a multihull, powered by a pair of common-rail diesels, and I asked the obvious question: How have these engines been, in your experience? His answer was telling. He said he was glad to have two engines on these catamarans because usually one of the two will have problems during the delivery — problems that he can’t solve. If you’re contemplating a voyage on a single-engine monohull, you would probably find that response unnerving, to say the least.

Rebuild or Replace the Auxiliary Engine?

As I stated earlier, the simple solution to your power needs may not be to replace the 25-horsepower with the beefy 75-horsepower motor. Depending on your boat and circumstances, you may still be able to get a currently compliant (EPA-wise) engine in the lower-horsepower range that still uses older technology. The dividing line at present is found at about 50 horsepower, depending on the manufacturer.

If you think you need more than that, you’re probably going to end up with an electronically controlled diesel engine with all the fixings — and a major series of modifications to your old boat will be needed to make the change.

If that’s the case, the possibility of rebuilding your existing sailboat auxiliary engine may make better economic sense, but only if the circumstances allow it. If you are merely trying to get a boat refreshed for resale within a year or so, the overhaul of your existing engine makes some sense. A rebuild typically will save several thousand dollars, compared with a full-on replacement. But you’ll only be able to enjoy a very limited warranty on the work, compared with the two- to five-year peace of mind that comes with a new marine diesel’s warranty. Further, realize that as the engine ages, parts become increasingly difficult to find; next time a repair becomes necessary, it may be impossible. If you’re planning on keeping the boat, in my view, a repower is the only intelligent solution.

Marine Diesel Engine Comparison

A search for sailboat auxiliary diesels yields results that would indicate there are really only seven brands: Yanmar, Volvo Penta, Beta, Westerbeke, Perkins, Vetus and Nanni, with Yanmar and Volvo Penta maintaining significant market share. Of the 24 sailboats in our BOTY mix this year, 11 were powered with Yanmars and 10 with Volvo Pentas. We had one boat with twin 20-horsepower Honda outboards, one with twin Nanni diesels, and one sailboat with an electric drive. You’ll probably read in online forums that most marine diesels are made by either Kubota or Mitsubishi, but that’s not quite accurate.

Yanmar produces all of its engines, and Volvo Penta manufactures its larger ones in-house. Smaller Volvos are produced by Perkins and given a Volvo-green paint job. Understand that Perkins uses the Kubota diesel as its base engine and then marinizes it to its own specifications. Perkins, which is a subsidiary of Caterpillar, is based in the United Kingdom, but also has some distribution here in the United States.

Nanni, a French company, uses Kubota, Man, Toyota and John Deere engines as its bases, depending on the horsepower. Vetus, with very limited U.S. exposure, has used Kubota, Mitsubishi and other base engines over the years. I can remember vividly a customer of mine years ago with a Vetus that used a four-cylinder Peugeot diesel as its base.

The bottom line today is that the volume of engines produced for the marine industry is quite small by industrial standards. Globalization has made it easy for manufacturers to source base engines for marine use that might also be used in tractors, generators and other relatively small machinery in both on- and off-road applications. With that in mind, it pays to check out the dealer and distributor network from both a regional and international perspective before you make a final choice. Beta, for example, has a significant dealer and parts network here in the U.S., so if you plan on cruising locally, parts and repairs should be easy enough to find. Beta, Yanmar, Volvo Penta and Westerbeke also offer a variety of engine-mount options to accommodate the various footprints that installers may encounter.

By comparison, if you opt to go with a Nanni, here in the States at least, repairs might not be that simple. I needed no less than 30 minutes and three phone calls to the Florida distributor to find out what the U.S. warranty covers. I still don’t know. I found the Australian distributor’s website, which mentions a two-year “plus one” guarantee, but the definition of “plus one” wouldn’t upload. On sailing forums, I found quite a few folks who complained about hard-to-find and expensive parts. It seems when Nanni marinizes, say, a Kubota engine, things like air-intake filters and other common service items are proprietary, and so replacements can’t necessarily be purchased at the local Kubota tractor dealer on some remote out island. Since the company is based in Europe, service and parts may be more available there.

For those who use their boats only occasionally and close to home waters, service and parts availability may not be a big enough issue to outweigh other considerations, such as cost. But if long-distance cruising is in your plans, it pays to carefully assess service and parts availability from a global perspective.

As for your modern electronic common-rail diesel engine, if that’s the way you must go, at the very least, stick with one of the two major manufacturers, Volvo Penta or Yanmar — and even then, good luck if you get hit by lightning halfway to Tonga. You’ll be hard pressed to find a service technician in a timely fashion, so carrying spare electronic components should be a serious consideration.

And a final note: For those of you who are on the last go-round with the venerable Universal Atomic Four gasoline engine, it’s time to switch to a diesel, if for no other reason than the continued availability of parts. If you want to stick with the Universal brand, give Westerbeke a call; the company still supplies two Universal engine models — the M3-20 B and the M-25 XPB — that are bolt-in replacements for the gas units. By the way, these are both Kubota-based engines.

Ed Sherman is the vice president of the American Boat & Yacht Council and heads its education division. He is a frequent CW Boat of the Year judge.

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Repowering Your Boat: What You Need To Know

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There are many considerations when starting a repower project, including some that are unrelated to the performance requirements of your boat.

These five below, should give you a good starting point from which to plan your shopping list.

Transom Limitations: Space and Weight

The physical limitations of your transom will dictate how much horsepower and weight you can put back there. While modern four-strokes are getting close to their two-stroke counterparts in weight, they still will add to the load at the stern. If you were not running the maximum-rated horsepower in your previous set up, you may have some wiggle room, and be able to absorb some extra weight without impacting seaworthiness. It's a good idea to check with your boatbuilder what the design limitations were before you start shopping. Weight considerations could limit you to DI two-stroke technology.

Space is more of an issue if you are running twins (or more) because some of the high-horsepower modern four-strokes need more width between the engines, but not always. Honda, for example, designed their four-strokes to fit the standard footprint for easy repowers.

In addition, with the increased horsepower ratings available today, you may wish to switch from twins to a single outboard configuration. For example, swapping twin-150s for a single 300-hp motor, in theory, will reduce both weight and drag, which should increase fuel economy without sacrificing performance. However, boatbuilders caution that the increased power and torque of these modern, power-dense outboards can be too much for transoms that weren't designed for it. A safe bet is to limit horsepower to the highest horsepower single engine configuration offered as original equipment. The boatbuilder should be able to go into greater detail.

Rigging: Time To Upgrade To Electronic Controls?

This is your chance to simplify your dash and clean up the console, as well as consider adding joystick control, if you are running twins. If you've got a large multifunction display, you may also wish to network it to your outboard(s) to allow it to display engine data. To do so, you need to look for an outboard that supports NMEA standard data outputs or one that offers a "gateway" converter that changes proprietary outputs into a data stream that your chartplotter can use.

Converting to joystick control will also require hydraulic steering, and a specialized command bus to talk to the joystick.

How you intend to use your outboard? If you do a lot of trolling or low speed operation, you may benefit from an outboard that makes use of fuel saving tactics like stratified combustion. If you run offshore or through an inlet to go fishing, you may benefit from electronic throttle controls combined with an outboard with instantaneous mid-range punch.

Maintenance Schedules

Scheduled maintenance intervals have a big impact on the cost of ownership during the life of the outboard. In general, DI two-strokes will have longer intervals between scheduled services because they lack mechanically-controlled drive trains that need adjustment every 500 to 1,000 hours. Although recently Mercury unveiled a 150-hp four-stroke that should not require valve adjustments at all during it's lifetime. Four strokes also need regular oil changes. But annual oil changes should be weighed against the operating cost of burning oil in a DI two-stroke.

Electrical Demand

The amperage output of most outboards has increased over the years, but if you run an electric trolling motor all day, or a suite of electronics while drifting or slow-trolling, the alternator on your outboard better be able to keep up. Check not only the rated amperage output, but also make a note of what the output is a low rpm, where it could half of what it is a cruising speeds.

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Michael Vatalaro is the former executive editor of BoatUS Magazine. He has a Pursuit center console, which he uses in the Chesapeake Bay.

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Thoughts on Repower

This article appeared in Soundings – April, 2003.

Repowering Your Sailboat

No matter how old your sailboat is, you still have the option of repowering. Stanley Feigenbaum of Beta Marine North Carolina – is the North American distributor for the Beta Marine line of engines, including the Atomic 4 replacement series. Beta specializes in diesel engines for sailboats and displacement powerboats, primarily in 10- to 75-hp range. Here Feigenbaum answers some common questions he fields from customers interested in repowering.

As the Owner of an older sailboat, when should I consider repowering?

Most people will repower their sailboats (or displacement powerboat) when its engine has died an awful mechanical death or when regular maintenance becomes too expensive. With an older engine, parts and labor costs for normal maintenance and repairs seems exorbitant. The $500 here and $800 there soon add up to a sizeable chunk of change, and make a new engine an attractive alternative. A complete rebuild of an older diesel or gas engine is within $1,000 to $2,000 of the price of a new engine, and the rebuilt powerplant sometimes retains its starter, alternator and transmission. A new engine will come with a complete warranty, so other than the oil, filters and the odd impeller there should be no hidden expenses for a good number of years. If your boat has an old gasoline engine, than a new diesel with its fuel economy will look particularly attractive.

What’s a common concern among owners debating whether or not to repower?

The cost. All too often a boat owner will put off the expense of repowering for many years. The hope is that he or she will sell the boat, and the engine will be someone else’s problem. What happens is the boat doesn’t sell, so the owner has to repower to attract a buyer. The buyer usually wins, as the previous owner still had to repower but never had the pleasure of the reliable power the new engine provides.

Can I replace my engine with a more powerful one?

Most people replace an old 20- to 40-hp engine with a new one of similar horsepower, though occasionally the call is for more power. Someone with a worn out 35-hp diesel (optimistically called a 50-hp by the manufacturer 20 or 30 years ago) says “ I need more power to move my boat. ” This is fine if the power can be put to use driving the boat, and charging the batteries and refrigeration system.

The problem comes about when the larger engine won’t fit the engine compartment, and the prop that it needs to work properly won’t fit under the hull. At Beta Marine we work with naval architects and propeller companies. These professionals have the knowledge that allows us to supply the correct engine and transmission ratio for a particular boat. We, and the boat owner, can then be assured that the propeller will fit the boat, and the engine’s power can be transmitted to the water. Ask if an engine/transmission combination will work in your boat. Most engines are available with a choice of transmission ratios, so choose what is best for your boat, and you will be happy with the result. Remember, diesel engine technology has come a long way in the last three decades.

How can I be sure the new engine will fit into my boat?

Measure very carefully, and do it twice. It is cheaper than trying to build new engine beds or redo the cabinetry. Some manufacturers supply engines with options for the feet (Beta Marine & Universal) so people with Atomic 4 engines can repower with diesel without redesigning the engine beds. These engines are no more expensive than those with standard feet, so why go through the added expense of changing the boat to suit the engine?

Will a new engine increase the value of my boat?

The answer to this question usually is no. If you were to look at an older boat with a bad engine or no engine, you would deduct that from the asking price. If you were to sell your boat at or near BUC value, then the buyer would expect a good, working engine. A new engine indeed will make the value of your boat a few thousand dollars. However, it will not increase the value by the price of the engine, and please don’t even think of recouping the labor involved.

What’s the typical cost of repowering a sailboat?

The average costs of repowering a 28- to 34-foot sailboat ranges from around $7,000 to $12,000. This doesn’t allow for V-drive transmissions, which always add to the labor cost because of the extra time involved. Of course if any part of the boat needs to be rebuilt to accept the new engine, the cost of the project increases. I have seen many older, cherished boats whose engine beds were found to be loose when the old single-cylinder thumper was removed. The beds had previously broken away from the hull, but the vibration they created hid the fact that they had caused damage.

On larger sailboats the cost of repowering is too vast to estimate. A boat that’s simple to work on, such as one with decent engine access, could be only $1,000 plus the cost of the new engine. On other boats, a Bristol 41.1 or a Valiant 40 for example, a mechanic is likely to have 80 to 100 hours in the job. Multiply that by the hourly rate to get your labor price, without yet allowing for the exhaust parts, control cables, and the like.

Does rebuilding an old engine ever make more sense than repowering?

It is usually uneconomical to rebuild a small engine that has been raw-water cooled for 20 years. Although the rebuild usually can be accomplished successfully, what often happens is that the saltwater corrosion in the block and head has taken its toll, leading to problems with water in the oil after a year or two. The only way to cure this, if it is a block problem, is to replace the engine. The boat owner has then paid for a rebuild at nearly the cost of a new engine, and now is faced with the cost of the repower as well. Sometimes it pays to spend a bit more and get a proper job.

Repowering Your Sailboat

by: JOE DEMERS

If your present engine is always hard to start, has constantly smoky exhaust, burns or leaks a lot of oil, is low on power, has coolant or water in the oil, or parts are difficult or expensive to acquire, repowering solves ALL these problems.

Installing a new diesel engine in your sailboat has many advantages. A new engine has the latest diesel technology. New engines are lighter, smaller, and run much smoother and quieter, with minimal exhaust emissions and superior fuel economy. The new engine and transmission will have factory warranties, with no parts supply problems.

You're also able to leave your homeport for far off destinations, confident in the fact that the new engine will get you home in a timely and safe manner. This greatly increases the utility and safety of your boat and removes the "will the engine start this time?" anxiety. After all, she is a "pleasure" boat. Remember, unlike a car, one cannot hitchhike home when your marine engine is broken.

Rebuild vs. Replace

Customers ask if rebuilding their present engine is financially feasible. It is usually not so. Parts can be expensive and difficult to find, if they're even available. Rebuilding an engine without rebuilding the transmission is a bad idea, as the transmission becomes the weak link in the powertrain.

Old raw water [salt water] cooled engines, such as the Volvo Penta MD7, MD11, Farymann A30M and Atomic 4 gasoline engine, are very poor candidates for rebuilding. They usually break during disassembly, due to advanced internal corrosion, and cannot be reassembled. Also, the internal water passages in the block and head are wasted away to a fraction of their original thickness, with a major and permanent engine failure inevitable. Most machine shops that rebuild engines will not touch salt-water cooled engines for these reasons.

There's also a world of difference between a professionally rebuilt engine and a "home rebuilt" engine. It takes a high degree of precision, experience, technical skill, and the correct machine and hand tools to correctly rebuild an engine. This means you must, at a minimum, hire a professional to rebuild the entire fuel injection system, engine head, and correctly inspect, fit, and install the other major components. This costs money that is better spent on a new technology diesel.

Considering these factors, most customers choose a new engine for their boat, which actually is the correct financial decision.

Selecting a New Engine

The first question a customer usually asks is, "How do I select the new engine for my boat?" We always answer with the following questions -

1] What make and model boat are we discussing?

2] What make and model engine is currently installed?

3] In what geographic area do you sail?

4] Are you a cruiser, or strictly a racer?

5] What electrical loads are aboard?

Answers to the above questions determine the engine we recommend. For example, if you sail on an inland lake with no tidal currents, you don't need a lot of horsepower to drive the boat. Conversely, if you sail offshore, where you encounter large waves, strong winds, and also need electrical generating capacity to operate radar, an autopilot, watermaker, etc., we suggest more horsepower, along with a larger alternator or two.

The trend for the last 15 years is to install more powerful engines in sailboats. Some customers want a powerboat when not sailing, and desire a large engine to drive the boat to hull speed, and to maintain speed when encountering wind and wave. In a displacement hull sailboat, this attempt is easily overdone.

Remember, the speed of a displacement hull (one that plows through the water, in contrast to one that skims over the water] is limited by the length of her waterline. Once top speed [hull speed] is attained, the boat cannot go faster, no matter how much horsepower is installed. This is because the hull has formed a bow wave, a stern wave, and a trough between them. The boat is sitting in a hole, and cannot climb her own bow wave.

Therefore, it will take "X" amount of horsepower to drive a sailboat with a "Y" waterline length to hull speed. We then suggest a bit more horsepower, for reserve power when fighting strong currents and waves. More power than this is not needed or desired, as the boat cannot go faster than hull speed. Why pay for horsepower that cannot be used to drive the boat?

One BIG limiting factor in pushing any sailboat is the diameter of the propeller. If your boat can only fit a 12" diameter prop, such as the Tartan 34C, more than 25 horsepower is a waste of money. This is due to the inability of the small prop to transfer greater horsepower to the water. Also, an oversized engine costs more, weighs more, and is harder to service since it fills the engine space more completely than a correctly sized engine.

Let's discuss the Catalina 30, an extremely successful design of 6000+ hulls built. Hull speed of this boat, with her 25-foot waterline, is a theoretical 6.5 knots. The boat needs only 12 horsepower to reach hull speed, under ideal conditions [clean bottom, flat water, no wind, correct transmission reduction ratio, and correct prop]. Now, let's add a bit more horsepower to ensure the boat can reach hull speed under less than ideal weather conditions. Sixteen horsepower is adequate. Twenty horsepower is ideal for this boat, as boat speed is maintained under most conditions, while also charging batteries. Remember, the boat is still an auxiliary powered sailboat, not a powerboat. If you must make headway under power into 25+ knots of wind, and the resulting waves, you need a powerboat...and a seatbelt!

Repowering your vessel is your chance to install the correct engine for your exact application. To maximize powering efficiency, the engine, transmission reduction ratio, and propeller must work together. Don't assume that your present transmission ratio and prop are making the most of your engine's horsepower. Many times when customers complain about poor boat performance, it's because the propeller's diameter, pitch, or transmission reduction ratio do not compliment the engine's power.

Your engine should be running at cruising rpm when the boat is at hull speed. Cruising rpm is usually somewhere between 85% to 95% of maximum engine rpm. This will allow the engine to develop its rated horsepower and operate the cooling system efficiently, and will correctly load the engine for maximum service life. There will also be a few hundred rpm in reserve, to maintain hull speed when encountering wind and wave.

If you intend to install an engine of "X" horsepower because that's what the boatbuilder did, you may be perpetuating a mistake. That's because it is very common in the boatbuilding industry to install an engine that was purchased inexpensively, regardless of its overall suitability for the application. One example is the Cape Dory 28, displacing 9,000 pounds. The factory sometimes installed a VolvoMD2B engine of 25 horsepower, weighing 505 pounds, which is WAY too much power and weight for the application. The boat simply cannot use all the available horsepower, and the boat is handicapped by the extra engine weight. A much more suitable engine would be one of 13 horsepower, as it has plenty of power to drive her to hull speed, such as the old VolvoMD7A. TheMD7A was installed in the heavier Cape Dory 30, and is smaller and lighter than the MD2B by 120 pounds.Modern designs such as the BetaMarine 13.5 horsepower engine weigh 195 pounds, resulting in improved sailing performance, particularly in light air.

Installation Considerations

Any new engine must be installed to the latest marine standards. This means only certified marine-grade materials be used for the exhaust, cooling, ventilation, electrical, control and fuel systems. These specialized parts and materials are not available at Home Depot. The American Boat and Yacht Council (ABYC; abycinc.org) publishes voluntary engine installation standards for small craft.

The most common mistake boat owners make when repowering is to duplicate the old exhaust system currently. This results in a new engine being installed to an outdated standard, and puts it at risk for major damage. A wet marine exhaust system is a critical installation in any sailboat. It must be designed and installed to prevent raw water from backflooding the engine, and also have minimal restrictions to allow the engine to freely breathe.

Backflooding is very damaging to any engine.Major repairs are likely if salt water enters the cylinders. This can occur when sailing (engine off) in a following sea, or when the boat is pitching or heeling, thus swamping the exhaust through hull.We prefer a through-hull with an integral flapper valve, as it provides another layer of protection against backflooding.

The ABYC says the exhaust through-hull must be installed where it will not be underwater during the normal operation of the boat. The ideal location is in the middle of the transom. If this is not practical, the through hull-should be located as high and as close to centerline as possible. The old practice of locating the exhaust through-hull on the counter is a bad idea, as it will be submerged whenever the boat is underway.

A waterlift type muffler must be installed to assist the engine in discharging the exhaust water up and overboard. The muffler is located at the lowest point in the system. Its primary function is to capture exhaust water when the engine is shut off. This will help prevent water from backflooding the engine. Its secondary function is to muffle exhaust noise.

Avoid the thin, blow-molded plastic mufflers, as they will melt should the raw water supply be interrupted. The old stainless steel mufflers corroded internally from hot salt water, and developed leaks. A heavy duty, heat resistant fiberglass wet muffler is ideal, as it is indestructible.

Exhaust system hose must be certified for that specific use, and should be secured using "T bolt" type hose clamps. These clamps are highly recommended for this critical application, and are far superior to worm drive type clamps. We always use 3M 5200 adhesive sealant on exhaust hose connections, to eliminate exhaust water "weeping" and any possible minor exhaust gas leaks. Ideally, there should be "soft wall" (no internal wire) hose between the engine and muffler, for maximum flexibility. The remaining hose is usually the wire reinforced and corrugated type, so it cannot kink when bent into a tight radius.

A vent loop, or siphon break, is needed on any engine that is installed at or below the waterline. Its function is to introduce air into the exhaust system, to break any siphon action that may occur when sailing. We prefer the minimally restrictive type, with stainless steel tubing and a plastic valve. It should be installed as close to centerline as possible, and at least two feet above the static waterline. We usually install them under the bridge deck. The exhaust hose should run vertically from the muffler, to the highest point in the exhaust system. We like to see the highest point well above the underside of the cockpit sole. From there, it should run downhill to the through-hull.

If room allows, an additional loop of exhaust hose can be located just inside the transom. This will force any backflooding water to work against gravity instead of easily entering the exhaust system. Alternately, a one-piece plastic exhaust part, shaped like a compact saxophone, can be installed for this function. If a marine check valve can be installed, it will assist in keeping that new engine from drowning. Remember, all exhaust components must work together to help prevent engine backflooding. A correctly designed wet exhaust system will have several of the aforementioned items to help prevent this potential engine disaster.

Fuel Tank & Systems

The location of the fuel tank deck plate has caused many problems. Many old boats have the fill located in the cockpit sole, which reminds us of a bathtub drain. Any water that enters the cockpit will attempt to get past the fill, and enter the fuel tank. We strongly suggest relocating the deck plate to a winch island, where standing water cannot accumulate over it. We prefer all stainless construction, as plastic can warp in the sun. All deck plates rely upon a rubber O-ring to seal out water - check yours for condition. There must be a ground wire of at least 6- gauge copper, electrically connected between the metal deck plate and the fuel tank, to remove any static electricity produced when refueling. Use only USCG approved fuel hose for the tank fill and tank vent. A shut off valve at the tank is also required.

The standpipe (fuel suction pipe) inside the fuel tank may have a screen installed. Remove it permanently, as they can clog and strand you at sea with a very difficult repair.

Standpipes are usually a bit shorter than the tank is deep. This was to keep any contaminants inside the tank, and have the engine draw off only clean fuel. It also ensured that during rough weather, the accumulated sludge would be stirred into the clean fuel, overwhelming the fuel system and leaving you with a non-running engine at a critical time.

We suggest the standpipe be extended with nylon tubing, to lay along the bottom of the tank. Now, your fuel filter will continually remove any contaminants, and maintain only clean fuel in your tank. A refinement is to pre-filter all fuel BEFORE it enters your tank with a funnel designed for such use. Racor makes several models that will remove all water and grit.

The fuel feed system should use US Coast Guard grade A1 marine fuel hose, which meets the highest standards for chafe resistance, fuel permeation and fire resistance. Copper tubing is not allowed, as it's electrically conductive and subject to work hardening, impact damage and leaks.

A fuel filter/water separator must be installed, as diesel engines MUST HAVE very clean, water-free fuel to operate. The Racor model 500 with clear sediment bowl is preferred. It's a simple, top loading design, and filter elements are common and inexpensive. Also, it will trap and hold a cup of water, to protect your engine's expensive fuel injection system. A drain is provided so you can manually remove water and junk BEFORE it can move along to the engine.

The Racor filter should be installed outside the engine space, where the fuel is not subject to engine heat, which can result in a loss of engine performance. Leave room above the unit for easy element removal and replacement.

Secure the fuel hoses to bulkheads with stainless clips that have rubber chafe protection. Marine-grade stainless steel hose clamps with an additional band of metal under the screw slots (called lined clamps) are ideal, so the hose is not damaged by the clamp.

The fuel return hose, from engine back to tank, should have a "U" orientation somewhere along its length to ensure the fuel injectors are not siphoned dry while sailing. The bottom of the "U" must be lower than the bottom of the tank. If overlooked, this important detail can result in an engine not starting after sailing,

Cooling Systems

The raw water cooling system can contribute to engine overheating, if the following details are ignored:

• A scoop strainer (mounted outside the hull) has no place on a sailboat, as they can force water past the raw water pump while sailing, fill the wet muffler, then allow water to backflow and enter the engine cylinders. They also will not allow bottom paint to be placed inside the through-hull, and cannot be easily inspected for barnacles or other restrictions. Much better is a common mushroom head bronze through-hull that is easily maintained and inspected, even with the boat in the water. A certified marine seacock, preferably bronze, and of ball valve construction, should be installed to ABYC standards.

• A ball valve, commonly seen just screwed to a throughhull, is a very poor substitute. We remove inferior or incorrect through-hull/valve installations, and insist the customer not compromise when keeping the ocean out of the boat! BEWARE the cheap ball valve designed for shoreside installations. If the boat should sink, the insurance company will rightly refuse the claim.

• A bronze raw water strainer, with clear bowl, designed for use below the waterline, should be installed inside the boat. The plastic type (designed for bait wells, fresh water systems, etc.) is not suitable for this critical application. The strainer should be located where it's easily observed and maintained. The hose between the ocean and the engine must be of wire reinforced, below waterline marine certified type, so it will not collapse under raw water pump suction and cause the engine to overheat. We actually saw a boat where the owner had used common garden hose, and he was dumbfounded when we immediately ripped it out.

Your engine can be plumbed to heat fresh water for cooking and showers. Heating this water is "free" and it will be available whenever the engine has run for about one hour. This requires the installation of a water heater tank with an internal heat exchanger. If the tank is located at the same level, or higher than the engine, a remote header tank must be installed at the high point of the system. This will ensure that the engine's cooling system will not get airbound, and possibly overheat. An ideal location for the remote header tank is just inside a cockpit locker, where it is easily observed and maintained. A translucent plastic coolant recovery bottle is highly recommended, as it will assist in purging all air from the cooling system and allow checking the coolant level at a glance.

Ancillary Systems

All diesel engines need lots of fresh air for combustion. Ideally, a blower, wired to the key switch and designed to automatically run and shut off with the engine, should be installed to create a minor vacuum inside the engine space.

The hot air suction hose should be located high and aft in the compartment, while the cool air intake hose should be low and forward, to completely ventilate the engine space. Alternators produce heat when operating, and the fresh, cool air provided by this system will contribute greatly to the service life of all components subject to engine and alternator heat.

An excellent upgrade from a 2-lever engine/transmission control system is a single lever control. This facilitates simple, intuitive engine operation, and ensures that the transmission can only be engaged when the engine is running at idle speed. That's important when approaching your slip a bit too fast! The control panel should be mounted where it can be reached and observed without leaving the helm. Otherwise, starting and stopping the engine and watching the gauges will be difficult and distracting.

The stuffing box (or packing box) causes many problems, mainly because it gets ignored. We like the traditional bronze type, with Gore-Tex packing. If the packing nut is correctly adjusted on a smooth prop shaft, and engine alignment is correct, it will not leak at any time. My personal Catalina 27 had a new stuffing box and prop shaft installed in 2007. I have done nothing since the installation, and it does not leak, period. We do not recommend the so-called "dripless" prop shaft seal. In our experience, they solve a problem that does not exist and we refuse to install them because they're unreliable. The bronze type is cheaper, easier to adjust and maintain, fire and impact resistant, supports the prop shaft, is simpler and MUCH more reliable. These characteristics are very desirable at sea!

The stuffing box hose (stern tube hose) should be replaced during a repower, for reliability. Use hose intended for this application - nothing else will do. Also install new T-bolt type clamps for this critical installation.

The cutless bearing supports the shaft, and is located just forward of the prop. Inspect it for wear or cracking of the rubber lining. If a new prop shaft is installed, a new cutless bearing is required.

Stainless prop shafts are now standard in the industry, as they are less expensive, stiffer, and harder than bronze shafts. The "overhang" (length of prop shaft between the cutless bearing and the prop) must be no greater than one shaft diameter, to avoid shaft "whip" and premature cutless bearing wear.

Your old prop shaft MAY be reusable, if it passes inspection. Most prop shops will check it for free. It should be inspected for straightness (within .003" along its length), corrosion and wear. Shafts can be straightened at prop shops, although it may be cheaper to buy a new shaft. Have the shop "fit and face" the new coupler to the shaft, so these parts rotate concentrically, to minimize vibration.

We recommend 2-blade props for sailboats, unless you must regularly fight strong wind, waves, or current. A 3-blade prop will provide more thrust under those conditions. The tradeoff is increased drag under sail. An excellent compromise is a 2-blade prop with large blade area. It is less expensive than a 3-blade, but will provide most of the thrust, along with the reduced drag of a 2- blade.

Diameter and pitch are the main variables when specifying a prop. Again, the engine horsepower, transmission reduction ratio, and prop must be correctly matched so they work in concert to efficiently drive the boat. Correctly specifying and installing a new engine and related components will ensure the utmost reliability, service life, and enjoyment of your vessel. For more information, visit soundmarinediesel.com.

Joe DeMers has been in the marine industry as a certified marine diesel mechanic for 30 years. He started his business, Sound Marine Diesel LLC, in 1997, and sells and installs Beta Marine diesel engines and generators.

The Complete Guide to Repowering Your Boat

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What does repowering a boat mean, should i repower my boat, boat repower options and considerations, how to prep a boat to repower, how to repower a boat outboard, how long does it take to repower a boat, how often should i repower a boat, is it better to repower a boat or buy new.

If you're tempted to buy a new boat because you're interested in an upgrade, you're not alone. While new boats are exciting and fresh, they're expensive, and you may not have the budget for one at the moment. If your boat could use some updates and you want to avoid buying new, consider repowering. This approach can be a more cost-efficient way to keep your current boat yet add the necessary updates to keep it running smoothly.

Whether you're repowering a pontoon boat or a fishing boat, you'll want to read a bit about repowering before you proceed. Use our guide for help thinking about the various aspects of repowering your boat and whether it's the right choice for you.

In short, repowering a boat means updating the engine and its subsequent features — you can either purchase a new engine or rebuild your current one. While the engine is certainly a large part of the process, the engine is usually connected to other features on your boat, like steering controls, gauges, fuel and battery systems and more. As a result, almost every function of your boat will feel upgraded.

The type of engine your boat has will partly determine how complex of a project you're taking on. If you're looking to repower a boat's outboard engine, the process will likely be quite simple because the engine is easy to access. If you want to repower an inboard boat, the engine is more difficult to access and is more likely to be connected to other parts of the boat, so the process becomes more complex.

If you're mechanically inclined, you may be able to do the repower yourself, though it's usually best to let professionals repower boat engines. With the proper tools and training, service professionals can ensure your boat gets repowered with less risk of damage.

While repowering older boats can end up being an in-depth project, it's a smart way to improve numerous functions and controls to keep your boat running longer for less money.

There are many reasons you might consider repowering your boat. If you need boating reasons to repower, consider how updating your engine can breathe new life into your boat. Doing so can make taking your boat out on the water a whole new experience, all without having to pay for an entirely new boat.

For many boat owners with aging boats, the body of the boat is still in good condition, but the engine may be racking up a substantial number of hours. When that happens, the engine is likely reaching the end of its life and is running inefficiently. A weak engine can cause the entire boat to run poorly.

When there's nothing wrong with the boat itself but the engine needs a reboot, it often makes sense to repower your boat rather than buy a new boat. If you're looking for more horsepower or better fuel efficiency, you should also consider how repowering can be more financially beneficial than buying new. 

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Repowering your boat is an opportunity to make necessary changes, though not every change will be beneficial to the way your boat runs. Repowering a boat is more than just installing a new engine — there are numerous aspects and different options for each aspect that you should consider.

Here are some important considerations when choosing to repower your boat:

1. Horsepower

Many people want to upgrade their boat's horsepower when repowering. However, you should be cautious if this is something you're considering.

Boats have horsepower capacities, and exceeding them can cause serious damage to the entire boat. Be sure to check what your boat's maximum horsepower rating is before you proceed with a repower. The set horsepower is the horsepower you should keep in mind when repowering, regardless of what you had previously.

Your boat will perform best at its maximum horsepower rating because the engine won't be struggling. This aspect often also results in better fuel economy, too.

2. Engine Brands

The most significant part of repowering your boat is replacing the engine, so naturally, you may want to consider other brands than your current one. You'll likely want to find the best motor to repower older boats so you know it'll work well. Changing the engine brand can mean more work to complete the project, but if you're unhappy with the brand's performance, warranty or another aspect of the brand, it may make sense to switch brands.

Switching brands typically requires the boat to be re-rigged, which will require more of a financial investment on your part. However, re-rigging your boat with a different brand engine is an opportunity to replace outdated controls, which is something you may need to do anyway.

While it's not as common now, boat owners used to switch from gas to diesel because it was cheaper. If you're thinking about how to repower a boat to a diesel engine, it may be best to avoid doing so. Today, diesel engines aren't as cost-efficient.

Additionally, repowering to a diesel engine is quite a challenging task. Repowering to a diesel engine typically requires your entire boat's system to be reengineered, which means the cost might not make it a viable option. If you're wanting to go diesel, consider finding a new or used diesel boat for sale instead of trying to repower your current boat to be diesel.

3. Number of Outboards

If your boat uses an outboard engine, you may consider changing the number of outboards you use. This is another aspect of re-powering you should approach with caution.

If your boat currently uses two outboards, you may be able to switch to one large outboard rather than two smaller ones. When changing the number of outboards on your boat, it's important to consider the weight of the motors and the space two of them take up. You should look for a new outboard that offers similar or more power at a similar weight.

Switching from one outboard to two may not make as much sense, especially because many single outboards today can power your boat just as well or better than two do. Additionally, trying to put two outboards where there was only one can raise several issues. For example, two outboards may add too much weight to the boat, there may not be enough room or your boat may lack the necessary structural support.

4. Controls and Instruments

Repowering your boat is a great opportunity to get everything updated, especially the controls. Like we mentioned earlier, switching engine brands may require you to change your boat's controls, but doing so anyway can improve your boat's performance and your experience.

From the throttle and steering to the electrical harnesses and cables, updating your system will make your new engine more enjoyable. Also consider how digital instruments can provide more information than old gauges, like fuel consumption and efficiency.

5. Joysticks

If you're repowering a bass boat or other fishing boat, you might consider adding a joystick control. Joysticks enable you to maneuver your boat at slow speeds with more accuracy. This can be extremely beneficial when docking or making slight changes in direction while fishing.

However, there are a couple of important factors to consider before adding a joystick. For example, when adding to an existing engine system, joystick systems work better with two outboards rather than a single engine. Additionally, installing a joystick system can be costly, so you'll need to determine if you can afford it and whether it's worth the investment.

6. Fuel System Components

Installing new fuel system components is highly recommended when repowering an old boat. Replacing your fuel hoses ensures your boat has ethanol-resistant, Coast Guard-approved hoses. Checking fuel components regularly and replacing them as necessary is crucial to maintaining your boat's engine.

Additionally, be sure to install properly sized hoses and fittings if you upgraded the horsepower. Components that are too small can prevent fuel from getting to the engine, hindering performance and damaging it.

7. Battery Systems

Depending on the engine and features you want to add, your current battery system may not be capable of powering the entire system. For example, outboards with power steering may require more power than your old battery can handle. In some cases, you may be able to replace old battery cables that may be corroded. Doing so has the potential to improve the battery system.

While doing a repower yourself can be challenging, if it's an outboard, it may be relatively simple. Boats like pontoons and many fishing boats use outboards, so if you have an outboard, you could do it yourself as long as you have the proper tools and knowledge. Consider the following process to learn how to repower a pontoon boat with an outboard engine.

Remove the Engine

Preparing your boat for a repower requires removing your current engine. If you have any hesitations about being able to properly remove your engine, it's best to consult a mechanic to help you out. This way, you won't inadvertently cause damage to the engine throughout the process.

To start, you'll need to prepare the old engine and various cables and wiring. There can be a lot of value in these parts, so if you're planning on selling them, be sure to keep them in good condition and neatly organized. Potential buyers and parts-seekers will look for individual items and entire cable systems, so even if something doesn't work, keep the parts because someone may see value in them.

First, the control, battery and steering cables should be disconnected. If you're reusing the steering and battery cables, be sure to set them aside so they don't get mixed in with the for-sale items. Next, carefully take out the controls, gauges and wiring harnesses. To make installing new harnesses easier during the repower, tie pull-cords to the ends of the wiring harnesses.

To finish prepping the engine for removal, drain all of the engine fluids. Drain the oil and remove the oil filter. Remove any other fuel filters and remember to drain the fuel lines.

Prepare a Gantry

Another important aspect of preparation is preparing a gantry. Since most engines can easily weigh up to 500 pounds, you'll likely need a system for lifting the engine off the boat's transom.

A gantry is essentially a support frame you can use as a crane to lift the engine. If you have a tree with a thick overhanging branch you can park your boat trailer under, this will make a great gantry. Your other option is to build a gantry with four legs, cross-braces and a traverse beam.

Stability and strength are crucial here to ensure the gantry can support the weight of your engine. Once you have a gantry ready, you'll want to tow your trailer into position so the outboard is centered underneath the branch or beam.

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With your outboard in place, it's time to remove it. For this process, you'll need a come-along strap. One end of the come-along will attach to the branch or beam and the other end will hook onto the outboard's lifting eye.

The location of your outboard's lifting eye will depend on its brand. You may find it mounted under the cowl, while others may lack one entirely. In this case, you'll need to purchase a lifting eye and screw it into the top of the engine.

With your come-along attached to the lifting eye, you'll want to ratchet the strap so there's minimal tension. With the strap tight enough to support the engine when it's loose from the boat, you can begin unscrewing the nuts on the engine mount. With the nuts removed, you can get the bolts out.

With a partner, slowly move the boat forward just a bit while the other person gently rocks the engine to loosen the bolts. It's crucial to do this step carefully and slowly to prevent the mounting holes on the transom from getting damaged. Damaged mounting holes will make it difficult to install a new outboard securely.

Once the bolts are removed, pull the boat away and your old engine will remain hanging from the gantry. To get the old engine out of the way, simply use the ratchet to lower it onto a truck bed or trailer to haul it away.

The process for mounting a new outboard will be similar, although performed backward. If you're installing an outboard with compatible controls to your current setup, the installation will be as simple as securing the engine on the transom and rewiring the controls. If you need to update your old controls, gauges and instruments, you may need to seek help from a repower dealer as these processes become significantly more complex.

The amount of time it takes to repower a boat will largely depend on the complexity of the upgrade, the type of engine and whether you're doing it yourself or having a dealer handle it. For example, an outboard repower could take as little as an afternoon, but repowering a boat with electric features and new systems will take more time.

If you have a dealership service do the repower, the time it takes will vary depending on their availability and readily they can get the necessary parts.

If you've bought a used boat, you'll likely need to repower it sooner rather than later because the motor will likely already have several hours on it. If the engine is well-maintained, you may be able to put up to 5,000 hours on it before repowering it.

However, most boat owners need to repower after 2,000 hours . While this may make it sound like you'll need to repower your boat often, for most boat owners who only use their boats seasonally, this could end up being 10 or more years.

The best way to know how often to repower your boat is to keep an eye on the hours you put on it and how it continues to run over time. If you notice it starting to run poorly, you may be looking at a repower sooner than that. Keep an eye on it and you'll know the best time to repower your boat.

In many cases, repowering is a more cost-efficient option for boat owners looking to upgrade. If your boat is still structurally sound but could use some more power, repowering may be a viable option. Luckily, there are financing options available whether you want to buy an engine to repower your current boat or decide to get a new boat altogether. If you're unsure of the best option for your wallet and your boat, consider having a service dealer give you a price estimate based on the type of boat and its condition.

Compare prices — if the cost of repowering is close to or exceeds the cost of buying a new boat, it probably won't end up being the right option. At that point, buying a new boat will be more reliable and may even have newer features you wouldn't be able to get installed on your old boat.

Learn About Boat Loans From My Financing USA

Whether you're repowering your current boat or looking to invest in a new one, you're likely looking for financing options. At My Financing USA, we can help you finance engines or a new boat entirely. We do the leg work for you when it comes to finding the best boat financing programs across the nation. We'll help you get pre-qualified and will only send you to one lender at a time so you can protect your credit in the process. 

With an entirely online process, you can sign documents electronically and receive funds fast. With our help, you could get your financing within two to three days and start your repowering project sooner or buy the new boat you've been admiring. Our application process is simple, and you can fill out an application in minutes to get started.

Would you like more information? Contact our friendly team today!

Additional Resources on Boats:

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• How to De-Winterize Your Boat
• Boat Maintenance: Everything You Need to Know
• Guide to Different Types of Boats
• How to Rent a Boat Slip

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Repowering A Boat

Today’s well-built boats are made to last. That means repowering—or updating the engine—will eventually need to happen if your boat is a long-term investment. What is more, preowned boats need repowering sooner than new boats. In either case, repowering extends the life of a boat regardless of age. That’s a good thing, and so are the choices that can make your boat perform even better.

Beyond the obvious cost factor, other questions should be considered. Packaged boats come standard with a specific horsepower, which can be lower than the maximum rating. Do you want more speed and performance? You can repower with the maximum horsepower and enjoy the benefits. Those include greater performance and possibly even better fuel economy.

Here are other factors to consider when repowering.

Update the controls

You update home and personal electronic devices with the latest technology, so why not upgrade the controls of the boat? Some controls sync with the motor so you can monitor and control the entire system on a touch panel display. An example is Mercury Marine’s SmartCraft. The benefits are total vessel integration through a complete suite of digital technologies. Those include Digital Throttle & Shift (DTS) to digital gauges, sensors, alarms and other onboard electronics. Put another way, SmartCraft’s intuitive features can make controlling the boat easier.

Update the instrumentation

If your budget allows it, consider updating to digital gauges and instrumentation. Digital gauges allow synchronization with total monitoring and control systems like SmartCraft. They aren’t just for large vessels. SmartCraft is available for Mercury engines 40HP and larger. Analog gauges retain their simplicity for quick reading. Those are compatible with all engines. An example of digital instrumentation is Mercury’s VesselView, which is designed primarily for saltwater boats with two or more outboards. VesselView allows you to display engine information, genset, sounder and much more. You can see rpm, speed, fuel flow and efficiency, temperature, trim and more. Up to four engines can be monitored with the intuitive, "at-a-glance" LCD screen. The VesselView suite of multifunction displays come in 4”—9” glass touchscreen versions.

Fuel systems and batteries

At the very least, update the fuel hoses with new Coast-Guard approved, ethanol-resistant hoses. It’s not the front and center of repowering, but update the batteries if you also upgrade to more power-needy digital control systems. Some newer outboards with integrated power steering and high-pressure fuel delivery systems also may require more battery power. Check the engine manufacturer’s specifications or ask your dealer for more information about updating the electrical system.

Update to a new motor technology

Should you update with the old guard twostroke or the newer fourstroke outboards? In the early 2000s, fourstrokes were deemed as the next coming of outdoor motor technology. Fourstroke outboards are quieter, idle smoother and are very reliable. Fourstrokes pollute less and get better fuel economy. In the early 2000s, they were associated with being heavier and requiring more service, though. Two- and fourstrokes are now approaching parity when it comes to weight and maintenance. The decision on which to repower with is easier. The fourstroke’s lubrication system has an oil pan and filter. With twostrokes, a drive train is unnecessary because valve trains (camshafts, belts, chains) are nonexistent. With fewer moving parts, the twostroke is lighter in weight and offers a quick, powerful holeshot. Internal engine parts are lubricated from oil mixed into the fuel. Decide based on which technology meets your expectations for performance and value.

Add a joystick

If the boat is compatible, a joystick is a wise investment. Mercury Joystick Piloting turns any pilot into a seasoned pro, regardless of docking skills. You can use the outboard system’s joystick to move the boat sideways, at an angle or even maneuver the boat through close quarters without having to use the throttles. The system really shines in current and windy conditions at the marina. Another cool feature is Skyhook, which uses information from the GPS system to keep the boat in place. It’s great for docking and even better for fishing. Skyhook can keep the boat in position without having to move the boat using the outboards. This is especially useful when drift fishing.

These are only a few of the questions you will face when repowering. Keep in mind that marine engines of today are packed with technology, which means there are many options available for repowering. Visit your nearest Bass Pro Shops/Cabela’s Boating Center for friendly, helpful and expert advice on all your repowering needs. 

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10 Questions to Answer Before Repowering an Outboard Boat

• By Jim Hendricks
• Updated: July 16, 2019

The thought of purchasing a new fishing boat always sounds tempting, but for many would-be buyers, the timing might not be right. If the propulsion system on your current boat is growing tired, however, the timing might be right for fresh horses.

Repowering a boat is a great way to extend the life of a fishing machine. Yet there’s more to consider than just bolting on new engines . You need to figure out how much it costs to repower your boat, and weigh a number of additional options. Here are 10 questions to ask yourself or your dealer, with answers offered by outboard experts.

Should I change horsepower?

“Look at the boat’s capacity plate to learn the maximum rated horsepower,” says David Meeler, marine-product information manager for Yamaha Outboards . “That’s the horsepower you should put on your boat during a repower, no matter what you had before.”

Boats perform at their best with the maximum rated horsepower, Meeler points out. Plus, you’ll often get the best fuel economy because the engine is not struggling. “Just because you have the horsepower doesn’t mean you have to use it all of the time,” Meeler adds. “But it’s nice to have it handy when needed, such as when powering over a big wave.”

Should I change engine brands?

The biggest reason to change is unhappiness with your current brand, be it related to performance, local dealer service or warranty terms. If you’re satisfied with all three, there’s little reason to change brands. If you do plan to switch, check out the local dealer and make sure you’re comfortable with the available service, the product and the warranty.

Should I change the number of outboards?

Changing the number of outboards is not a good idea, says Evinrude product manager Jason Eckman. “It’s very complex and involves lots of fiberglass work to prep the transom for such a drastic switch,” he says. “Also, adding another outboard can add too much weight to the stern, or the transom might not have enough width or structural support to accommodate another engine.”

If you want to go from a single to twins for offshore safety, that issue is hardly relevant today. “Reliability of today’s outboards is such that you should not be afraid to go 30 to 40 miles offshore with a single outboard,” says Meeler.

Should I get new controls and instruments?

It’s a good idea to update everything — steering, throttle and shift, cables, electrical harnesses, battery cables, and instruments, says Larry Teeling, product category manager for Mercury Marine . Consider the steering. “Why struggle with an old, worn steering system with your new outboard?” Teeling asks. Similarly, a new engine with old controls and gauges will only dampen your experience.

Digital instrumentation has also come a long way in the last 10 years, Teeling says, offering information that old gauges could not provide, such as fuel consumption and best speed for fuel efficiency.

Should I change to another outboard technology?

The technology aspect of a repower has become less impactful over time, contends Teeling: “In the early 2000s, four-stroke outboards were associated with being heavier and requiring more maintenance than two-strokes. That’s no longer the case.” As two- and four-strokes approach parity in terms of weight and maintenance, the key is to select an outboard technology that makes your boat perform the way you want and maximizes its value, says Teeling.

Can I add a joystick control as part of a repower project?

Joysticks offer intuitive, slow-speed steering, allowing anyone to dock a boat like a professional captain. While original-equipment manufacturer systems with joystick controls, such as Yamaha’s Helm Master and Mercury’s Outboard Pilot , are not available for aftermarket installations, SeaStar Solutions Optimus 360 power-steering system (which includes a joystick control) can be added to an existing boat.

The decision to add it as part of a repower project boils down to three factors, says David Greenwood, product planning manager for Suzuki Marine . “First you need to have multiple outboards, as such systems won’t work with a single engine,” Greenwood points out. “Secondly, consider your experience level and the size of your boat. If you lack experience in docking a relatively large boat — say over 30 feet in length — in tight quarters, a joystick can be very helpful.”

The third factor is the price, Greenwood says. An Optimus 360 system can range from $18,000 to $22,000, plus installation costs. “Is the benefit worth the investment?” Greenwood asks. “Only the boat owner can answer that.”

Should I install new fuel-system components?

The short answer is a resounding yes, says Yamaha’s Meeler. “I recommend that boaters replace all of the boat’s fuel hoses with new Coast Guard-approved, ethanol-resistant hoses with every repower, if not more often,” he says. “This is also the time to make sure you have a 10-micron water-separating fuel filter for each engine.”

If you’re upgrading to higher horsepower, check the engine manufacturer’s specifications to ensure that you install a fuel hose and fittings with inside diameters (e.g., ⅜ inch) sufficient to sustain the engine’s fuel needs at wide-open throttle. A fuel line or fitting that’s too small can starve the engine of fuel at the upper rpm range, not only hampering performance, but also leaning out the fuel-to-air ratio, a condition that can damage an engine.

Will my old battery system be sufficient?

The answer depends on which engine you choose. Some outboards with integrated power-steering systems and high-pressure fuel-delivery systems may require a more robust battery system. Check the engine manufacturer’s specifications or ask your dealer.

“You should also replace the old battery cables with fresh ones,” says Evinrude’s Eckman. Old cables might be corroded inside, causing too much resistance, lowering the voltage delivery, and increasing amp draw to excessive levels.

Which color should I choose?

Evinrude, Mercury and Suzuki each offer color choices in their outboard lineups. Yet color is mostly cosmetic, says Mercury’s Teeling: “Matching the color of engines to the boat has become quite popular.” In warmer climates where water spots develop quickly, white outboards are more popular, says Suzuki’s Greenwood. “White does not show water spots as much as a darker outboard will,” he observes.

What should I do with my old engine?

You can advertise your old engine for sale, but your main stumbling block will be moving a large, heavy outboard off your boat and onto the buyer’s boat. This is where a dealer can help, according to Sara Pines, public relations director for Honda Marine . “Consult with your local dealer about your old engine,” Pines says. “Often, they are willing to assist you in the selling of the old engine.”

Finally, the most important ­question to ask yourself is, “How long do I plan to keep my boat?” The cost of new power, related upgrades and installation charges can range from $10,000 to $80,000 or more. “For that kind of investment, plan on keeping your current boat for the next 10 years at least,” says Evinrude’s Eckman.

Yamaha’s Meeler echoes that ­sentiment. “The first thing I ask anyone who comes to me with repower questions is, ‘How much do you love your boat?’” he says. “The answer will help you determine what the future holds — new power or a whole new boat.”

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A Guide to Repowering With Outboards

The author provides a thorough and detailed guide covering all you need to know before moving ahead with a repowering project.

As many of you might have gleaned from reading my boat and motor review articles for the past four decades, if you don’t have the budget to purchase a new boat, the best alternative is to look for a quality boat brand that’s four to seven years old. If you can find one with potentially tired outboards that are coming off or just past their warranty period, you can likely negotiate a good deal on the boat’s final asking price and then consider purchasing fresh power to replicate the “almost new” boating experience, but at a fraction of the cost. Plus you can get a fresh five- to seven-year warranty on the new engines, protecting your investment and limiting any future unplanned “surprise” out-of-pocket costs.

Personally, I have been involved with a total of 17 outboard repowering projects since the late 1980s, and I am currently managing number 18 as you read this. Having experienced both a number of smooth sailing and unplanned disastrous moments during the course of these repowering projects, I should have enough real world guidelines to create this repowering guideline from memory. When Fisherman readers reach out to me about the art and science of repowering, I usually suggest that they sit down and ask themselves some tough and thought-provoking questions, many of which are detailed in the following paragraphs.

However, to make this outboard repowering guide as informative as possible, I took the added step of reaching out to three of my local Long Island dealers who collectively manage over 100 repowering projects each season, just to get some truly professional advice. Special thanks to the good folks at Albertson Marine in Southold, Spellman’s Marine in Hampton Bays and Suffolk Marine in Babylon for sharing their expertise. They had plenty of great advice, so let’s get right into it.

Is Your Boat a Candidate for Repowering?

This is the big question that will determine the success or failure of your potential repowering project. As you ponder the final answer, be advised that this generic question can be broken down into a number of smaller queries. Many older boats are eliminated by a number of different factors when considering repowering, specifically: How old is the boat? What is the current physical state of the transom? (Are there any soft spots, water intrusion issues or rot?) What is the physical state of the rest of the hull and deck? What is the transom weight limitation of the powerplant? Where are the boat’s scupper locations when wet with the current engine and where might they be with the new powerplant? What is the horsepower limitation of the transom, as detailed on the boat’s safety/capacity label? Once you generate some real world answers to these questions and analyze the data, you will be in a much better position to determine if your planned repowering project is a go or no-go.

Basic Boating Equipment Compatibility Checklist

Once you have determined that it’s time to take the next step in the repowering process, be advised that the rest of the boat’s mechanical systems need to be in good working order before you continue. If not, you might have to replace certain systems like the mechanical throttle and shift cables; the control box; the steering system, which includes items like the helm, mechanical steering cable, hydraulic cylinder, hydraulic hoses and fittings, plus the steering helm itself and/or the steering wheel. Putting a new engine on the transom and using 15-year-old cables and an archaic steering system to control it is akin to putting old tires on a new car – it just doesn’t make any sense.

If you have an old single or dual cable steering system, you might want to upgrade to a hydraulic, tilting-helm unit. If you have an existing hydraulic helm unit, is your current cylinder compatible with the new engine? If not, that’s an added expense for the parts and labor that will increase your overall project cost. What about power steering, to assist your hydraulic steering unit? You’ll need to find a place to put this, plus that’s yet another added cost item. You get the picture, it’s wise to plan ahead to keep project surprises and cost over-runs to a minimum.

Yet another area of concern is your boat props. Depending on brand, gear ratios, material (S/S or aluminum), number of blades and the condition of what you currently have, you may or may not be able to use your existing propeller(s) on the new outboard. New stainless steel props are not cheap and will cost you anywhere in the $550-$750 range per unit, depending on the manufacturer. One of the things I like about Merc props is that you can run them on every brand of outboard with the right hub kit. They also feature a removable polymer FloTorque II hub design that ruptures on impact with anything solid (saving your prop blades) and can be easily changed in the field with a few basic tools in five minutes or less. I have a half dozen different Merc props that I use for my boat performance tests and they are all ready and anxiously waiting in the wings to spin their magic on my new 250 V8 to help me max out its performance.    

Do Your Batteries Have Enough Juice?

While it’s always a good idea to refresh your batteries when repowering your outboard(s) – remember that “old tires on a new car” analogy – your new engine might actually require something with added 12-volt capacity. This is especially true if you are going from a mechanical engine to a digital version, like I am doing with my current project of upgrading my 2006 EdgeWater 228cc to a Mercury 250 DTS (digital throttle & shift) V8 four-stroke. It’s important that you read the operations and installation manuals PRIOR to making any final decisions on battery replacement, to ensure that whatever it is you are getting, it meets and exceeds the standards that the new engine requires. Current engines require more juice for running their onboard computers and sensors, digital fuel injection and digital network systems, among other requirements, so be advised.

As a case in point, my EdgeWater 228cc’s current source of 12-volt power is delivered by a pair of Interstate “wet” Series-27 dual purpose cranking/deep cycle marine batteries, with 750 marine cranking amps and a minimum reserve capacity of 160 minutes at 25 amps. In contrast, according to my owner’s manual, my new 2020 Mercury 250 V8 FourStroke requires an AGM (absorbed glass mat) “dry” battery that is rated for 800 marine cranking amps and a minimum reserve capacity of 135 minutes at 25 amps. Bottom line, I am probably going to have to upgrade my batteries to the dry AGM type and might have to go with a slightly larger 31-series battery to get this done. It’s always better to have a little more juice than a little less. This is especially true when you are starting up your big outboard 30 to 40 miles offshore, after a day of wreck hunting or shark fishing and working your big screen electronics for most of the day. There is no sound quite like the outboard engine coughing to life when it’s time to head for home.      

Is Your Fuel System Up to the Task?

It’s always a good idea to check all of the components in your fuel system when entertaining a repower project. These include the fuel lines from the tank to the fuel filter, the lines from the fuel filter to the engine, the vent lines, the fuel fill lines going to the tank from the deck fuel fill hardware, the seal on the fuel fill cap and most importantly, the fuel tank itself. It’s a general rule that an aluminum fuel tank will last approximately 20 years in the harsh marine environment. Nowadays, the next gen fuel tanks are either coal tar coated, painted with an epoxy primer, or manufactured from gasoline-resistant polymer, extending their useful lives out on the briny. But if your boat is more than five years old, there’s a good chance that it was made from anodized aluminum. My 1999 EdgeWater 185cc’s tank was fine, with no leaks. But if I had to change it tomorrow, the boat features a recessed gas tank hatch that can be removed to access the tank. That modular concept is still practiced by some top tier boat builders, but that number is dwindling with every passing model year. Why? It’s more work to build, fit, assemble and seal different fiberglass components compared to just making one part. But the problem is, once the tank goes bad, and it’s tucked below a one-piece fiberglass sole, you’ll have to take an electric saw to your cockpit and cut it out to pull the tank, creating a big mess and necessitating some expensive fiberglass repairs afterwards. I upgraded all of my critical fuel lines and installed a stainless steel framed fuel filter when I purchased my EdgeWater 228cc five years ago, so that should be one less thing to worry about when my dealer installs the new Merc 250 in the coming weeks.        

How’s Your Boat Wiring?

Both of my current EdgeWaters were a tale of two disparate worlds. The original factory wiring was harnessed, loomed and color-coded, with a detailed explanation of each wire’s function and destination point in the boat operator’s manual. This was not the case for all of the accessories that both of the original owners had added on after the fact. I wound up ripping out all of the aftermarket wiring, keeping the original EdgeWater wiring runs intact, but also added new Blue Sea 12-volt circuit breaker accessary panels that drive all of my critical electronics. I wasn’t thrilled with the original panels, which are now 21 and 14 years old respectively and at some point in the next year, will probably replace the existing accessory panels and breakers with completely new equipment. There are a number of vendors that will replicate your original panels, complete with function descriptions and boat brand logos, but more on that in a later article.

I am installing a new 6-gang Blue Sea Weatherdeck accessory panel on my EdgeWater 228cc to replace the 4-gang panel I installed on the boat when I bought her back in 2015. This panel will control my Simrad GO12 MFD, a Si-Tex Sea Temp Gauge, a Standard Horizon VHF, a ProSpec sound system, my new Mercury VesselView engine info gauge, plus a Furuno RD-33 GPS navigator. All of my super-critical info is on a new, high-quality circuit breaker panel that I will wire and route myself. The benefit of this is that if something goes wrong with my electronics offshore, I’m the one who installed it, rigged it and knows where each wire goes and what it does. Many of the professionals that I interviewed for this article recommended to leave the engine wiring sacrosanct and not tap anything electrically off of the gauges or the key switch. If you need additional wiring hookups for accessories or networks, install a dedicated power bus or attach it to a clean breaker position on an existing accessory panel.          

Analog Engine Information in a Digital World

One of the upgrades you will need to consider when repowering is what to do with your existing engine support gauges? Twin, triple and quad engine setups used to require at least a pair of instruments for each engine, but no longer. Yamaha introduced their series of keypad 6-inch and touchscreen 7-inch multi-function displays that totally solved this problem, concentrating all of this electronic info into one or two gauges and freeing up a significant amount of dash space. Their Command Link Plus series now takes networked NEMA2000 info and shares it with every MFD that is connected to the electronic trunk. I am losing two 3-3/8-inch gauges from my 228 EdgeWater’s old Yamaha F225’s instrument array (tach and speedo) and replacing them with a single 5-inch VesselView gauge (They also currently offer 7-inch, 9-inch and 12-inch displays.) from Mercury for the new 250 DTS (digital throttle & shift) V8 outboard that is in the process of getting rigged as you read this. This allowed me to install a larger accessory panel and consolidate a bunch of the vessel wiring into the new network. It also enables me to display some of that engine data on my GO12’s screen via the network if I so desire. The bottom line is this. If you are going from a mechanical/analog engine to a more current mechanical engine, you might be able to use som e of the old gauges and you might not. If you need digital info, the gauges will need to be changed. If you are evolving from a mechanical engine to an electric/digital platform, the gauges will probably need to be replaced by a multi-function display. You will also need to install a new throttle control box (with additional wiring harnesses required) and a key switch, add a NEMA2000 network, along with a few other system links that will allow seamless communications between all of these different parts. Translated – be sure to add the cost of these extra items to your repowering budget, plus the labor to install them.  

How Long Does It Take?

This is one of the “magic” questions of the repowering process, since ultimately, the amount of time that the dealer/installer spends on your engine replacement will be multiplied by an hourly rate that will be in the $125-$150/hour range, depending on where you call home. When trying to prognosticate the amount of time it takes to derig and install a new outboard engine, one of the dealers that I spoke with had a simple rule. One eight-hour day to take the old engine and wiring off, one day to install the new engine and one day out on the water to break it in and test it out with a variety of props. That’s 24 hours of time. Another dealer mentioned that if a boat owner was going from a mechanical engine from brand A to a newer mechanical model from the same manufacturer, this process could probably be done in half that time, typically 10 to 12 hours. If the boat owner were to go from a mechanical engine to a digital engine from the same manufacturer, the timeframe increases to the 15-

to 20-hour benchmark, due to the deletion and addition of a greater amount of accessory gear (electric control box and key switch, networks, new gauges, etc.). If you’re going from brand X to brand Y in your engine swap-out, you’ll probably have to add four to five hours of extra time to every one of these scenarios. Predictably, twin, triple and quad engine installations add more time to the process. You really need to get a good handle on the labor/installation end of the project to be able to predict the true bottom line cost.

There’s a good chance that your engines are worth something on the used market, especially if they are in good running condition. I was able to sell my used Yamaha F225 outboard that was original equipment on my EW 228cc in only a few days. Same was true for repurposing the Yamaha S130 two-stroke that was on the EW 185cc. When it comes to derigging your boat prior to installing a new outboard, anything that you can do yourself will save dealer rigging time and money. Be advised that some of the new gear might not fit in the old holes, which will require field modifications by either yourself or your installer/dealer, once again adding to the bottom line project cost.      

Some Final Thoughts

If there’s anything that I’ve learned with the events that my family has endured over the past few years, it’s that life is short and things can change in the blink of an eye. One of my wife’s favorite expressions is, “eat the cake, buy the shoes, and go on that vacation.” It is precisely this logic that compelled me to get that new Merc digital 250 V8 for my 14-year-old EdgeWater 228cc. I’ll let you know how it all works out, but I am ready to get her wet and catch some fish this season! If you have any engine repowering questions, reach out to me at [email protected] . 

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18 Reasons for Repowering an Outboard Boat

• By Kevin Falvey
• Updated: February 8, 2021

Repowering your boat ranks right up there with buying a new boat. For many, myself included, repowering is an exciting time in which a boat that suits me perfectly becomes even better. That’s especially true today because new engines deliver more benefits than older ones.

Just what do you get when you repower? Certainly, increased reliability is one aspect. But how else will you benefit? Should you sell or trade up to a new boat instead?

Having just repowered my 23 Regulator with a new 250 hp Mercury FourStroke outboard, I’ll present these issues and more from a fresh, first-person outboard owner’s perspective. We have sterndrive and inboard repower stories in the hopper, but many of the reasons why apply here.

The Candidate

A boat that suits your style and needs makes a good repower candidate. Many times as life changes happen, such as a marriage, kids leaving the house, or a new career, our boating needs change. Before you repower, make sure your current boat still suits the way you boat. Sometimes, buying a new or another boat (which you may repower) might make more sense for you. My center-console still fulfills my needs, which consist of about 80 percent coastal fishing and 20 percent tubing, beaching and otherwise day cruising. So, appraise your boating needs honestly.

If it does suit you, and you want to repower, make sure that it is structurally sound. You may or may not be qualified to assess this yourself, and a marine surveyor—or at least a knowledgeable and trusted friend or dealer—should be brought in to render an opinion before you proceed with a repower. More reputable dealers, such as Hampton Watercraft and Marine, which performed my repower job, will not proceed unless they deem the boat structurally sound. Some areas of key concern are the transom and the stringers. My 1997 Regulator, with its fiberglass grillage system and composite transom, needed no structural work. In any event, the need for structural repairs does not eliminate a boat from repower contention, but it needs to be ascertained so that repairs can be factored into the total cost of the job. A new transom might be a $4,000 job, as an example.

Besides structural work, your candidate boat should be assessed for the suitability of its systems. The new Mercury V-8 FourStroke I repowered with requires batteries rated at 800 cold-cranking amps, and that required me to upgrade to a new pair of Optima Blue Top series batteries (about $700). I also installed new battery cables. Additionally, I elected to keep my boat’s existing hydraulic steering system—power steering is great, and a benefit I’ll discuss further along—because I wasn’t willing to give up the space required for the steering pump and motor, given the limited space for such systems aboard my older, cut-transom boat. The choice to upgrade steering or to retain existing steering provides those repowering their boats with an option to save both space and money. For example, single-engine power steering costs about $1,200 in major parts, plus installation; a twin setup starts at $1,600 or so, plus installation. And if you are going with twins—or triples, quads or quints—know that joystick docking and maneuvering is a feature you might consider when repowering your boat.

Finally, you may have to reconfigure your helm’s gauge array when you repower. Mercury—as well as other engine-makers—offers digital displays and gauges that fit standard gauge holes. (And you can choose analog gauges and controls to save on cost.) These offer great functionality, and are especially suited to tight helms or where less time and expense to install are priorities. In my case, I opted to move from analog gauges to touchscreen multifunction displays, in the form of Mercury’s VesselView displays. This required a network backbone to be installed in the boat, for one thing. For another, it necessitated fabricating a completely new helm panel, a task I completed as a DIY project prior to delivering the boat to the installing dealer. A quality, full-service dealer will be capable of performing this task as well, and you should ask about it and to see examples of their work before committing to the repower. Such jobs will be billed by the hour and for parts and materials.

A new engine or engines may be your opportunity to increase horsepower or to change the number of engines. In the first case, you cannot repower your boat with an engine or engines that exceed its rating. No reputable dealer would ever do that, and no insurance company will write you coverage if you could get it done. So, remove having the world’s fastest Acme Waterbug 27 from your repower wish list.

My Regulator is rated for twins up to 400 hp, though I have been running it happily with a single 250 hp for many years. In deciding to repower with a single 250, I considered the increased reliability of engines; the weight of the new engines and the effect of that weight on the boat’s self-bailing ability, as well as performance and economy; the cost of owning one versus two engines; and the cost of owning a more powerful single engine. For me, with my boat and my intended use, the single was the right choice. I have run the boat with other engines and in both single and twin configurations. I realize not everyone is privileged with the access to boats that I enjoy, but if you seek out boaters at a local marina with similar boats, they will often be happy to take you out on a brief demo ride. A good dealer may also provide access to stock or customer boats for a sea trial, perhaps after a deposit is laid down, before you make your final decision.

In my case, the new outboard produces the same power as the previous boat, but weighs 90 pounds less and is a V-8 instead of a V-6. My boat is now a bit faster and a bit more economical, and there is another quarter-inch between the waterline and the scuppers.

My choice was right for me. Your choice may differ depending upon your circumstances. The point is to weigh these factors because these decisions must be made thoughtfully if a repower is to be successful—successful meaning that it includes you being happy as well as all the rest of the factors.

The Benefits

Most of the time, brand-new power under factory warranty delivers confidence and reliability, restoring fuller peace of mind to the boater. That’s great. It’s also obvious. What other reasons are there for repowering your boat? Well, certainly I’d have to also include pride in ownership, the savings of not buying a new boat, and the enhanced resale value for your boat. More tangible examples of things I directly benefited from after repowering follow.

My boat is 3 mph faster at wide-open throttle (43.2 vs. 40 mph) and delivers better economy at cruising speed, burning 8 gph at 22 mph (3,500 rpm) and 13 gph at 30 mph (4,200 rpm). And boy, is it quiet. I mean, it’s not just 2 decibels quieter while cruising than previous engines I’ve owned on this boat, but it sounds better too, emitting a deep, throaty note that appeals to this child of the muscle-car era. Every boating friend I’ve had aboard has commented positively about the way my new engine sounds. The most astute of them have also noted the lack of clunking while shifting, a result of the FLO-Torq SSR HD prop hub. Mercury actually has a lab devoted to a process that it calls NVH (noise vibration harshness). Newer engines offer smoother shifting, and a quieter, more pleasant audible experience while running.

Some other physical attributes that I consider beneficial include the ability to check the engine oil without removing the cowl. Open the Top Cowl Service Door—it pushes open like a fuel door on a car or truck—and the dipstick and oil fill are right there. This hatch also conceals a big lever handle that allows unlatching and removing the cowl one-handed. It comes off and goes back on easily. Once off, you’ll find neat features, like a maintenance schedule sticker you can scan with your phone and more. The freshwater flush attachment is located where it is easy to access whether you trailer your boat or keep it in the water. Maintenance is easier with a new engine.

But most of all, a new engine or engines are an opportunity to bring your boat into the digital age, and with that comes many benefits, from the aesthetic to the functional to the just plain cool. A NMEA 2000 (N2K, or Merc’s version, called SmartCraft) backbone will be installed in your boat, creating a network into which the new engine(s), controls, gauges and displays, as well as other equipment, such as stereos, fish finders and plotters, and a host of onboard sensors, can all be added for easy monitoring and control. For instance, I can display a host of engine data onscreen or on any of the other screens aboard that I’ve networked. I can mix this data with mapping, fish finding, autopilot and more, all depending upon my preference. Want big tachs and fuel info while running? Swipe the screen. Want stereo control? Swipe it again. Control over tow profiles for watersports? Just swipe and it appears. Additionally, with the right accessory plugged in, I can access these functions, in Mercury’s case, via the VesselView Mobile app. It turns my wireless device into a backup gauge array and/or a second station. The system provides alerts for maintenance such as oil changes and fuel filters, and can monitor ship’s systems such as CO monitors, tanks and more. Moreover, the networked controls provide push-button starting (so you can hide the key switch, if you like), and also enhance security because the engine will not start—it cannot be hot-wired like an older outboard—unless the key fob is on board. So, repowering nets you greater monitoring and control of everything, from fuel economy to the CO detector in the forward stateroom, plus provides several levels of redundancy and adds a measure of security.

When running the boat, a networked, digital engine such as my Mercury 250 FourStroke offers a host of benefits. For instance, there’s ActiveTrim, which automatically trims the engines to suit the circumstance, based upon GPS boat speed (competitive systems use engine rpm). I’ve been running outboards for about 45 years, and I can’t beat ActiveTrim. For 90 percent of my boating, it’s set it and forget it—the system trims the engines exactly as I would. As experienced boaters know, proper trim is key to maximize fuel efficiency. ActiveTrim can be turned on or off at will, and though it works fine out of the box, you can set the profile—the range of trim—and customize it to suit your boat.

Digital Throttle and Shift (DTS) is Mercury’s name for digital controls. But by any name, these provide some great differences compared to cable controls. Digital control handles move at the touch of a finger, and the levers don’t fall back and throttle your engine down due to cable tension and boat motion. Also, you can adjust rpm in fine increments using the digital display, which I find great for trolling and really dialing in a precise rpm for long cruises on open water. This works hand in hand with the Adaptive Speed Control my new outboard offers, a feature that maintains rpm even as load changes. For me, that means that while running in a following sea offshore, the engine doesn’t bog down and require me to accelerate on the back of every wave. If you cut tight turns or tow skiers, you’ll find the same thing—the engine maintains rpm. So, let’s add increased and easier boat control to our list of repower benefits.

There’s more. Tow Mode makes it easy to pull your skiers and riders with more precision, every time. My new engine’s alternator outputs a whopping 85 amps max and 20 amps at idle, and the engine automatically bumps up the idle rpm if it senses low batteries. Couple features as diverse as these with the others mentioned, and that’s at least 17 reasons to repower.

Oh, my new outboard also looks great, and it is available in a range of colors, as are those from other engine-makers. Feel free to add in bragging rights as another reason to repower.

Dealer Does the Install

Gone are the days of buying outboards in a crate and having the dealer load them in your pickup. Unless you buy used engines—which can be a good deal—the dealer will be installing your engine. It’s the only way to get a warranty, for one thing. And today’s outboards are one component, albeit a large one, of a total boat system. Go into a repower project with this in mind.

Sell or Trade Your Old Engines

I never have a problem selling used outboards. There is a ready market for them and, generally, you’ll get more money for them in a private sale as opposed to trading them in or having the dealer broker them for you. (Example: I sold my nine-year-old 250 for $5,000 last winter.) You can often get a better price on the new power if you show up without a trade-in motor and with a boat already derigged. If your buyer can back his boat on a trailer right next to yours, you can use an engine hoist/dolly to lift and move the outboards the few feet between boats. (See boatingmag.com/repower2020 for more details.)

Of course, your outboard dealer will be happy to either sell your engines for you or offer to take them in trade against the new sale. This is easier and quicker, usually, and there can be sales-tax benefits that apply to trades. Check with your state for local ordinances.

• More: Boats , engine repower 2020 , Engines , mercury marine , outboards

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