More of this Feature • Part 1: Gen Zen • Part 2: Gen Zen continued
Related Resources • Maintenance Editorial Index • Maintenance Q & A Index
Elsewhere on the Web • Northern Lights/Lugger • Onan

Years ago I chartered a Tolleycraft for a cruise around Washington State’s San Juan Islands. Although the boat had seen considerable use, she was a sturdy old girl and eminently reliable, with one notable exception: her genset. Located in the lazarette, right under an indifferently sealed hatch, it was constantly showered by sea water. Consequently, the thing looked like it had just been dredged out of some sunken World War II U-boat. And ran like it, too.

The charter operator claimed to be scrupulous about genset maintenance, which to him consisted solely of annual oil changes and fixing the set when it didn’t run. As a result, just about everything on my charter boat’s unit was leaking, rusting, loose, held together with duct tape, or some combination thereof, and not surprising, it started infrequently and ran with the assurance of a cardiac patient in a marathon.

Gensets have thankfully become a good deal more reliable and durable since then, but they still need care if you want them to start promptly and run without interruption. You know the major things you need to do to make this happen, like changing the oil and zincs, but there are other small maintenance tasks that are often overlooked, which also ensure that your genset will be trouble-free. To find out what those are, we asked the people who should know: genset manufacturers.

Years or Hours? Changing the oil and filter according to the manufacturer’s recommendations seems like a no-brainer, but are you sure you know what those recommendations are? Most intervals are expressed as a combination of calendar time and engine time—say, one year or 100 hours, whichever comes first. According to Greg Pressman, Onan’s service manager, when it comes to oil changes, boaters often concentrate on the time and ignore the hours. “Usually they change the genset oil when they change the engine oil,” he says. “They forget that gensets often get a lot more use than mains.” Make sure you heed those words “whichever comes first” for all service recommendations.

Cool(ant) Change. Even boaters who maintain proper oil-change intervals often forget that coolant also should be changed periodically. According to Kohler, you should change yours every 400 hours or six months. That’s because coolant degrades over time, even when the genset isn’t being used. When this happens, it can no longer perform its many duties, which include elevating the boiling point of plain water, lubricating the circulating water pump, preventing oxidation, and minimizing mineral deposits that naturally occur in water. All the manufacturers we spoke to also say that whenever possible, you should flush the system with fresh water after draining but before adding new coolant.

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