Please help me advise a friend whose boat I was looking at today trying to
get the engine running.

10 HP 2 cylinder Volvo diesel in an Albin Vega

Last time he started the engine, there was a buzzer like noise from behind
the switch panel but the engine started and ran. Not sure if buzzer noise
went away or not, I wasn't there.

Next time, there was the same buzzer noise but nothing else, not even a hint
of starter trying to go.

I went to look at it today and found that there had been a small fire inside
the elderly mechanical voltage regulator, not enough to keep it from making
a nice warning buzzer sound as one of the toasted relays chattered but
clearly enough to render it useless for anything except a doorbell.

Question: Would it be foolish to just swap in another regulator and see what
happens? Judging from the terminals, it's been fairly moist in it's
location. Could it have just gone bad on its own or is there likely an
underlying problem.

Battery is 12.9 volts but we didn't have time to dig any deeper.

It looks like kind of an oddball set up. Manuals he downloaded from the
Internet for the engine and voltage regulator say that it has one of the
combination starter / generators which I assume is the long, dual belt, unit
on the side. There is also an alternator that looks alike an addition from
the style of the mounting frame.

--
Roger Long