I agree with Paul...most boat fires are caused by electrical problems, usually DC. However, AC can be a problem, too. If you've ever spent much time around a liveaboard
marina, you've seen lots of horror stories, with haphazard wiring to dockside plug-ins, melted 30A connectors, etc.
In 1984 I moved aboard a seven-year old 43' houseboat, which was to become my primary home for the next 15 years. The PO told me there were "some electrical problems". Indeed, there were!
The boat was outfitted with a full-size kitchen refrigerator
, a 4-burner with oven electric
stove, a 20-gallon hot water
heater, a large RV-type air conditioner/heater in the main cabin
overhead, and assorted other 110VAC lights and appliances
All these circuits were routed to a standard household-type fusebox. Fuse sizes generally were appropriate for the respective circuits (except the stove...see below). Wire size was adequate, if not tinned copper marine
wire. However, believe it or not the entire fusebox -- except for the lighting
-- was connected directly to one of the boat's two 30A outlets!!!
In other words, it was easily possible to try to draw 20A for the air conditioner/heater, plus 15A for the hot water heater, plus 5-10A for the refrigerator
, plus 30A or more for the electric
stove (which, it turned out, never got hot because it had 220V elements installed and was connected to a 110V circuit!).....for a grand total of 70A or more!!!
And, we all know that the 30A connectors typical of small boat use are not really capable of handling 30A at all, except perhaps when conditions are absolutely favorable: new, clean tight connections, low ambient temperature, etc. Typically, if you try to routinely draw 30A thru a 30A "marine" connector, it's gonna heat up badly and will soon have a meltdown. Worse, the 30A splitters in common use for 3-phase systems are connected to a 50A breaker on the power pole, so protection is totally inadequate from that source.
learn about and be very careful about your electrical systems onboard, both DC and AC.