It's my impression that "start circuits;" i.e. the starter really doesn't
care about the voltage. Double the voltage and the no-load speed is
doubled, but under load it will pull the voltage down to whatever back EMF
corresponds to the starter speed. (The relays/contactors will have to have
the proper coil voltage, but that's a cheap conversion.)

Boats and electricals don't go together well at all. Simpler is more likely
to keep working.

Roger

http://home.insightbb.com/~derbyrm

"CyberSam" wrote in message
news:nAbIf.23932$Eq.3771@trnddc02...

The start circuit is 24V and the majority of the accessories will be 12V;
instruments, trim tabs, lights, radio, etc. I'd like to run a 24V
alternator
to charge a pair (in series) of 8D batteries. Ideally I'd like to have a
pair (in parallel) of deep cycle marine batteries for the 'house' load. I
realize now I may need to run two alternators, but I was just wondering if
a
single unit (that puts out both 12V and 24V) is available.