I'm just back from my weekend course on Boat Electrics, complete with my certificate to prove it.
Of course the certificate doesn't prove I had to pass anything - just that I showed up! However, it was a great course run by Tony Brooks at Reading College (part of Thames Valley University). We not only covered basic electrical theory on engines and on domestic systems in the boat, but we also, in small groups, got to wire up all the electrical bits of the engine - starter, alternator, glow plugs, solenoids and relays, warning lights and dashboard meters etc. Not only that we built a small domestic circuit with lights, a motor (eg for a pump), fuses etc, then coupled the two circuits together for charging purposes using a split charge system. Finally we did a lot on battery planning and management and on diagnosing faults. My brain is now officially full!
If you have a boat, and you don't have a clue on electrics, you should go. Well worth the money.