Generator service intervals are usually written for a unit that runs a modest number of hours a year. The boat that anchors out on summer weekends with the air conditioning running through the night doesn’t fit that picture. A generator carrying AC all season piles up hours fast, and the standard “annual service” timeline can leave you well past due by August without the calendar ever looking alarming. If you run your generator hard in summer, the interval that matters is hours, not months.
We’ve written about spring generator failures and about marine generator service generally. This post is specifically for the owner whose generator is the hardest-working diesel on the boat all summer.
Hours add up faster than you think
Do the arithmetic on a real summer. A generator running overnight to keep the AC going, ten or twelve hours a night, across a few weekends a month, stacks up a couple hundred hours in a single season without much trouble. A boat that cruises for a week or two on top of that, generator running most of the day and night, can log several hundred. That’s a full service interval, sometimes more, compressed into one summer. The owner who services “every spring” is changing oil on a generator that’s run a year and a half’s worth of hours since the last one.
Oil takes the worst of it
A generator runs at a steady load and a steady speed for hours, which is hard on oil in a way that the stop-and-go life of a propulsion engine isn’t. The oil shears down, picks up combustion byproducts, and loses its protection on a schedule set by hours, not by the calendar. Push past the hour interval because the season is young and you’re running an engine on tired oil right when summer heat is already working against it. On a heavily used generator we’d rather see the oil changed mid-season than wait for next spring. This is the same logic behind oil analysis and service intervals on the main engines, and it applies even more to a generator running long, steady hours.
The cooling system under continuous load
A generator running continuously through a hot night is cooling itself the whole time with warm inlet water, in a tight space, at a steady load. Impellers wear, zincs deplete, and heat exchangers foul on the basis of hours run, and a hard summer runs a lot of hours. The impeller that would last two seasons in a lightly used generator can be cooked by one heavy one. Checking the impeller, the zinc, and the raw water flow partway through a hard season is reasonable, not paranoid.
What heavy summer use should look like
For a generator that carries AC all season, we think in hours. Oil and filter at the manufacturer’s hour interval regardless of the date, which for a hard summer can mean a mid-season change. Impeller and raw water inspection partway through the season rather than once a year. Zincs checked on the same hours-based basis. Air filter kept clean, since a generator in a hot enclosure needs all the airflow it can get. None of it is complicated. It’s matching the service to how the unit is actually used instead of to a calendar that doesn’t know how your summer went.
If your generator is the hardest-working engine on the boat in summer, it should be serviced like it. We set up hour-based service schedules for heavily used generators and handle the mid-season work as part of marine generator service. Call us at (609) 242-8448 and we’ll build an interval around how you actually run.