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With normal maintenance and regular TLC, a genset can thrive for a long, long time

prm-Help Your Genset Live Forever

Here’s how to get the full life expectancy from yours.

Most gensets live lives of quiet desperation, shunted into a far corner of the engine room or, even worse, stuffed under the cockpit sole, where they’re ignored until the power goes out. Life is often short for a genny treated like this. But you can save your genset from this ignominious extinction, while keeping it happy and healthy, with just a bit of effort. While you can’t really render your generator immortal, despite the title of this column—“forever,” as used here, means until you sell your boat—if you give it the attention it deserves, your genset will most likely reward you with thousands of 120-volt-filled hours.

Because the genset is relatively small and not nearly as impressive as the vessel’s main engines, and it’s usually mounted someplace inconvenient, boat owners frequently fail to provide the maintenance it requires. Don’t be one of those people. A genset is more complex than a propulsion engine, even though the latter may have many times the horsepower. Comprised of an internal combustion engine (ICE) driving a generating unit, usually an alternator, a genset needs TLC on both sides. Taking care of just the ICE isn’t enough, but it’s where we’ll start.

Like all internal combustion engines, whether gas or diesel, your genset’s ICE needs pristine fuel, plenty of fresh air, an ample flow of cooling water and clean lube oil in the crankcase. If there’s an anti-siphon valve on the raw-water intake, clean it while you’re fitting out in the spring, or at least once a year if you boat year-round. Change sacrificial anodes when they’re half gone. If you have a gasoline ICE, change the plugs once in a while. Stick to the maintenance schedule in the owner’s manual. Inspect the ICE frequently, even if it means removing the sound shield; more about the pros and cons of shields below. Deal with rust and corrosion right away: Find the cause, usually a water leak, and fix it. Clean off loose rust, and repaint using appropriate engine paint. I coat rust with Ospho before repainting. It stops further rusting by turning the iron oxide into iron phosphate. Repainting is the important step, though.

Check the exhaust mixing elbow yearly—it’s where raw water is injected into the exhaust for discharge overboard, after passing through the heat exchanger to cool the freshwater system. A seriously corroded mixing elbow can let water backflow into the exhaust manifold and then into the engine via an open exhaust valve. This can bring an otherwise healthy engine to an untimely end. You need to remove the exhaust hose to check inside the elbow, an easy job for you (or your mechanic). You can inspect the exhaust hose at the same time. It’s worth the cost and effort.

Check the zincs in your generator’s heat exchanger on a regular basis.

Check the zincs in your generator’s heat exchanger on a regular basis.

Keep the Water Off

So much for maintaining the ICE, but what about the generator side of the genset? For advice, I contacted Bob Hansen and Fred Knowles at Hansen Marine Engineering, Inc., in the seagoing town of Marblehead, Massachusetts. Hansen and Knowles teamed up to start the company in 1975, and today they are the largest U.S. distributor for Westerbeke gas and diesel generators and the sole worldwide distributor for Westerbeke industrial/fire rescue generators. After 45 years of dealing with gensets, these guys know plenty.

Ninety-nine percent of the causes of genset failure can be traced to the operator, said Hansen. “They don’t run them, they don’t service them, they let water get on them.” Many outboard-powered center consoles now have gensets installed under the cockpit, where water can drop onto them and cause problems. “Don’t put the generator under a hatch,” said Knowles. “Hatches leak, and leak a lot, when the deck gets wet.” The generator should be installed under solid deck, with access through a nearby hatch. If the generator’s already under a hatch, added Knowles, renew the gaskets and place a cover over the generator to keep it dry. And ventilate: Aside from combustion and cooling needs, a steady flow of fresh air will help keep the space dry.

A generator under the cockpit shouldn’t be mounted directly on the stringers, said Knowles. Instead, it should be placed on a plywood base plate to keep bilge water from splashing up into the wiring. If the genset is placed way aft, the base plate should extend all the way to the transom—otherwise, when the boat’s powering up, bilge water can slosh aft, hit the transom and splash up onto the generator. “With all the electronics on them, modern gensets are like heart monitors,” said Hansen. “They don’t like water.”


Sound and Fury

Many skippers won’t have a genset onboard unless it’s in a sound shield. A shield not only dampens the noise, it also protects the genset from dripping water and dirt, a bonus if the genny’s in a locker or under the cockpit. On the other hand, you have to remove or at least open the panels on the shield to check the oil, look for fluid leaks, etc. Add the often awkward placement of the genset, and the tendency of most folks to take the path of least resistance, and a generator in a sound shield often gets less attention than it should. “The number one failure in sound enclosures is exhaust-hose burn through,” said Knowles. “Routine inspections are recommended.”

Check the tech specs in your owner’s manual, and you’ll see the alternator needs a lot more air for cooling than the genset’s ICE needs for combustion, and as Knowles said, more air is better for keeping things dry. But the sound shield is most effective with a minimum of openings, so the airflow is restricted in the pursuit of lower decibel readings. Because of this, always use the proper sound shield, the one that’s been engineered with the genset’s requirements in mind. Don’t restrict the air vents, and don’t stow gear around the genset that can block the vents. Have you ever cleaned out the air vents in your sound shield? I didn’t think so. Give the machine a chance to live a long life by providing it with not only cooling water, but cooling air, too.

If your genset’s mounted in the engine room, and the engine room’s properly noise-insulated, think about getting rid of the sound shield. The genset will get plenty of air and run cooler, and it’ll be easier to maintain. Leave the base of the shield in place; you have to lift the genset to remove it, making an easy job difficult, and it makes a nice drip pan. If you want to keep the shield, check its foam insulation every year or so—the foam lasts a long time, but not forever.

Genset maintenance

Use It or Lose It

Give your generator plenty of exercise, even if you don’t need the juice, but don’t run it unloaded; that’s not good for any engine. Check your owner’s manual for advice regarding recommended loading. “Run the set for at least an hour at a time to dry it out and exercise the engine,” advised Knowles. Don’t start the generator under load: Turn off all the AC breakers when shifting from shore power to ship power, turning on each item as needed once the generator is running. And never shut off the generator with a load on it, or you can damage the electrical components, added Knowles.

If you have a new genset, get off to a good start by following the manufacturer’s recommendations for break-in, just like you would a new propulsion engine. Sloppy break-in practices, like running without sufficient load or overloading (look for black exhaust smoke), can catch up with you later on. Break-in lets the piston rings seat properly against the cylinders; ignoring break-in can score the cylinders and cause excess oil consumption (blue exhaust smoke). Most new engines require about 50 hours before they’re completely broken in, but the first 10 or 15 are critical. After the break-in period, many engines will require the attention of a mechanic for fine-tuning, such as adjusting the valves, re-torquing the cylinder-head bolts, etc. Read the manual for specifics.

Finally, download your genset’s installation manual from the manufacturer’s website. It has more information on system components and their assembly than the owner’s manual does, along with detailed drawings. Knowing how the genset should be installed will help you maintain it and also help troubleshoot problems. You might discover that the original installer made errors that will affect the function and longevity of your genset.

And you can learn obscure things. For example, I found a couple of installation manuals from different manufacturers that recommended installing the genset with its crankshaft parallel to the vessel’s centerline, not athwartships, but with no explanation why. Fred Knowles said the reasoning is that the boat will roll more degrees than pitch, so the generator engine will be less likely to lose oil
pressure when mounted fore and aft. “But,” he added, “there are as many placed both ways.”

More important than crankshaft orientation, however, is how often you apply a dose of TLC. Don’t leave your genset to waste away in oblivion—give it the same attention as your main engines, and
chances are it’ll be cranking out 120 volts for years to come. Or at least until you sell your boat, which is long enough. ρ

Beware the Scoop

Sometimes even boatbuilders drop the ball when installing gensets. Bob Hansen told me of a new boat that came to him with a genset that had failed after only an hour of operation. Upon hauling the boat, he discovered the builder had installed a forward-facing scoop on the raw-water intake, a no-no (in all but specialized situations) that’s clearly warned against in every installation manual.

What’s the problem with a scoop? When the boat’s moving but the genset isn’t running—a common situation—the scoop picks up seawater and forces it through the cooling system and into the waterlift muffler, where it stops: The scoop doesn’t create enough pressure to push the water through the muffler and overboard. (When the engine is running, exhaust pressure does that.) Instead, the water fills the muffler, then backs up into the exhaust manifold, where it can flood the cylinders. Crank the engine with water in the cylinders, and hydraulic pressure makes something break.

According to Fred Knowles, not only should there be no forward-facing scoop, but an electric valve might be necessary to ensure seawater doesn’t enter the cooling system: When the engine’s shut down, the valve is closed. The exhaust discharge must also be routed to keep seawater from backfilling the exhaust system and thus filling the engine.

This article originally appeared in the December 2020 issue of Power & Motoryacht magazine.