Gensets spend long periods idle, often live in the lowest, wettest part of the engine room, and get less attention than the main engines. Yachting magazine's list of common faults and the generators Pascoe found on surveys point at the same handful of checks.
Starting power
Yachting magazine calls lack of starting power the most common generator problem: a dead battery, dirty or loose connections, or a breaker switched the wrong way. They're simple to fix, and they're also the first thing to rule out before blaming the generator.
Where to look. The genset start battery and its connections, the breakers, and a cold start.
Fuel filters
Because gensets sit unused for long periods, the fuel sits too, and Yachting magazine says clogged fuel filters are very common. Symptoms are rough idling, trouble picking up revs, hesitation or stopping. It notes the problem is especially common on gasoline gensets with ethanol fuel, which also troubles carburettors. It recommends carrying a spare filter aboard.
Where to look. Filter condition and date, water in the separator bowl, and how the genset runs under load.
Raw water
If the genset overheats, Yachting magazine says to check for a blocked intake and then the raw water strainer.
Where to look. Water flow at the exhaust outlet with the genset running, the strainer, and the impeller replacement record.
Mounting, drainage and access
Pascoe's surveys show generator installations that do the damage:
- Mainship 350 Trawler: the generator stuffed under the cockpit deck, hard to service, mounted so low the base was wet and rusting badly, with the steel sound box suffering because the aft bilge had no proper drainage.
- Bertram 36 Moppie: a cramped engine compartment where the 8 kW Kohler generator takes up much of the space between the engines, under heavy seating modules that owners won't lift to inspect.
Where to look. How high the genset sits above the bilge, rust on the base and sound box, standing water underneath, and whether you can reach the genset to service it.
Carbon monoxide
A running genset produces carbon monoxide. ABYC A-24 covers CO detection on boats. Check that CO alarms are fitted in the accommodation, in date and working, and that the genset exhaust outlet isn't placed where fumes can be drawn aboard.
What to check on a marine generator
| Area | What to look for | Source of the concern |
|---|---|---|
| Start battery and breakers | Charge, connections, switch positions | Yachting magazine |
| Fuel filter | Clogging, water, spare aboard | Yachting magazine |
| Raw water | Flow at the exhaust, strainer, impeller | Yachting magazine |
| Mounting | Height above bilge, rust on base and sound box | Pascoe, Mainship 350 |
| Access | Room to reach and service the genset | Pascoe, Mainship 350 and Bertram 36 Moppie |
| CO alarms | Fitted, in date, working | ABYC A-24 |
Writing it up
"Generator: mounted low in the aft bilge with the base and sound box frame rusted and standing water beneath; the bilge section has no drain to the main sump. Recommend the bilge drainage is corrected and the generator mounting assessed and treated before corrosion damages the frame." Record the genset make, model and hours.