Re: name that alternator! and other questions
I'm not aware of a marine electrical place around here that does this kind of work... they seem to all be the "install new radar" kind of marine electrical places, which I guess actually makes them marine electronics places. I took your advice and went to an alternator repair shop. They told me the alternator was putting out voltage, but conjectured that the brushes might be at the end of their life and thus intermittent and not putting out as much current as they should. A new alternator was $150, and having them rebuild the old one was estimated as similar, so I just bought the new one.
They explained that one of the wires -- the one that goes into the square-ish plug connector -- is "excitation", and provides 12V from the ignition to enable the alternator. The other mystery wire is the tachometer. They were not able to identify the mystery can-shaped component from my photos.
The new alternator is a World Power Systems 8625N, for anyone who cares. I can't find anything about it or the manufacturer online, but the guys at the shop told me it outputs 65A, which seems like plenty. They conjectured that the old alternator was about 50A.
Of course, while installing the new one, I dropped the big mounting nut into the bilge, and it being stainless, I can't use a magnet to find it... guess I need to make a trip to the hardware store in the morning. And then hopefully the new alternator actually solves my problem.
Thank you all for your help.
1979 Gulfstar 37 Laissez Faire