I have been researching DC motors to produce 12v @ 20+ amps at about 800 rpm. I see these golf cart generator/starter motors might work.
What do you know about these motors? Can they produce 20-25 amps 12v DC power and at what rpm’s. My application is to produce power from a turning engine 1-1/4″ shaft on a sailboat when sailing. I can produce about 800-900 rpm’s using a 6:1 pulley ratio shaft to motor at 6-7 knots.
Sounds like you are trying to re-invent the wheel. Several companies make an off-the-shelf water turbine that is self-contained and you just drop in a fast moving stream or pull behind a boat to generate electricity.
Since the internal generator and propeller drive are designed to rotate at the correct RPM for the typical speed through the water you are talking about, you do not need pulleys, belts, or drives, and all battery charging controls are built-in. These units are light weight, small, and specifically designed for this application.
Check with any of the solar suppliers that advertise in the magazine.