What Is a Marine Generator?
A small diesel power plant on board producing 220V - the heart of a comfortable, air-conditioned boat, but also the grumpiest bit of kit if it is not run often enough.
A marine generator is an enclosed unit with its own small diesel engine and alternator, producing 220V on board. It is seawater-cooled, so it has its own impeller, heat exchanger, exhaust elbow and waterlock. In short, it needs looking after much like a small main engine.
If you want air conditioning, an electric hob and heavy charging loads, the only real source at anchor is the generator. Its nature should also be understood: diesel engines like a decent load, and a generator run constantly at low load (under 20%) will age sooty, glazed and faulty.
Maintenance summary
Treat it like a small main engine: follow the same schedule for oil, impeller, fuel filter, anode and elbow.
Run it under load: a generator that spends hours running just a few lights does itself no favours; loads should be grouped together and run hard.
Its own cooling chain: the main engine’s impeller may be changed, but the generator’s can be forgotten for years; the same schedule applies to it too.
When deciding whether to buy or upgrade, ask the honest question first: is your load profile really generator territory, or would the lithium + inverter + solar trio give you both silence and lower maintenance?