After some thought...if a particular boat's systems were kept strictly like those of a car, that is: 12VDC alternator charging a battery (or batteries) that run only 12VDC appliances, then I'd have it made.
I have a good bit of experience with automotive electrical systems.
However, throw in solar and/or wind charging, put a charge controller in there, plus the 12VDC alternator, then throw in the odd 110V AC appliance and the inverter(s) required, and my ignorance starts to show.
Still though - I think I'll take your advice about a 12VDC course; no such thing as too much knowledge. And one never knows when a new instructor will give you a new way of looking at things or share some golden tidbit that he/she has picked up from personal experience.
As an aside, it's always bothered me, when working with cars, that one can ground something to a metal frame...that's rolling around on rubber tires. Mystical, that is. :P