Jim:
A company here in Texas sells wind generators, very nice powerful ones, for $600 new. I have one but yet to install it....been too busy or lazy or bothI would much rather have that than the generator and cost should be about the same.
At 8 knots it supposed to put out 2.5 amps and at 20 knots it's supposed to put out 23 amps. The blades are a little under 3' and the motor weights 40 lbs but that's do-able on most boats.
The generator was a tad under $200... I would rather do the wind thing too but i can't shell out $600. I would rather have the $400 in my pocket for now... Plus i can run my microwave man!