Chris,

I see you found my neighborhood cyber bar. Have a beer and keep an eye out
for flying pool cues and bottles.

The good news is that no one has jumped up to say that the problem must have
started somewhere else and a new regulator will just self distruct in the
same way. Could still happen but, if it was common, that's what we probably
would have heard.

The other good news is confirmation (recognizing that you have to take all
NG stuff with a grain of salt) that the generatior part of the dynastart was
not being used and the alternator is an addition. That means a separate
regulator and solonoid, readily available and not terribly expensive, are an
option.

What people are calling a starter solonoid isn't really. A solonoid pushes
the drive gear into place on some starters then disengages them so they
won't be turning and generating power when the engine is running. (Standard
starters must do this because there is no way to cut off power to the field
windings). When I was flying, an important step after starting was to turn
on power to the panel in special steps watching the ammeter to be sure the
starter (Bendix mechanical engagement / disengagement in this case) had not
remained engaged generating power that would fry the entire avionics stack
when the engine was brought up to speed.

The "solonoid" in this case is a simple, although large, relay that lets
battery power go directly through the large cables between the battery and
starter so you are not trying to start the engine with all the juice running
through the little starter switch. My engine doesn't have one so you can
sometimes get away without them at these small starting loads. Still a good
idea though. You can find these hanging on the rack at NAPA.

The "solonoid" / starter relay you buy will probably be physically identical
and from the same assembly line as the units I used to buy for the airplane
but at 1/6 the cost without the FAA tag. It should be mounted as close the
the starter as possible. One peculiarity of them is that, if the engine is
hard to start, and you run them too long, they will get hot and soften the
plastic liner of the electric coil and the plunger will stick. This may
leave them on and sending battery power to the starter while the engine
runs. The starter then becomes a generator and all hell breaks loose in the
electric system. Lots of pilots have died trying to land planes with smoke
filled cockpits because the FAA won't allow a safer alternative to be
installed. They also may not engage the starter next time or only engage
after you bang on them a while to shake the plunger loose. Buy two while
you are in NAPA.

You can't put a standard starter on your engine because there is no way to
engage and disengage it. However, since the Dynastart unit is designed to
be voltage regulated, you can disable it as a generator through that
circuitry and need to figure out how this was done. If this was done inside
the now fried regulator, a short that caused it to resume putting out power
while the engine was running is a prime suspect for your problems. If this
unit ever dies, you are going to be faced with the fact that only another
one from Volvo will work. I would remove it right now and have it
overhauled. If the brushes have worn down (remember, it runs all the time
the engine does), it would be an expensive thing to have missed. A
competent tech can also probably permanently disable the generator function
internally.

I would also remove the alternator and have it checked. Any car garage can
do this although they will probably send it out. If it is bad or about to
go bad, it would be a shame to have it undo all the hard work you are going
to put into getting this put back together.

Don't try to do this yourself until you have traced and tagged every wire
and produced a complet schematic of what you have now and how it will be
after modification. Few people could make up a system like this on the spot
in a rocking boat working in that tight space.

More good news: you are going to know a lot about boat starting and charging
circuits by the time this is done.

--
Roger Long