On Sun, 05 Apr 2009 20:36:52 +0000, Larry wrote:

Your electrical loads may be exceeding the capabilities of the
intermittently rated cheap alternator on your boat. Skip completely
cooked a brand new alternator that WASN'T rated for CONTINUOUS DUTY on
Flying Pig from a electric dealer in Charleston. I found out from his
experience most alternators are INTERMITTENT duty, designed to recharge
starting batteries, not power full time electrical loads. Those
cheaper, open frame, car-type alternators are all intermittent duty.
They'll put out 120Amps....for 10 minutes before overheating....not 54
hours on a voyage. The current rating is simply the maximum current to
expect, PEAK CURRENT, not average.

For the better part of a century, big central station alternators have
been hydrogen cooled. Hydrogen is a significantly better conductor of
heat than air. I wonder how the price per Watt compares to small ones.

Casady