"Dave W" wrote in message
...
Watts to HP....In 1492 Columbus divided the year in two and converted
watts
to horsepower. 1492/2=746watts/hp

Several smart answers on conversion of units, but none on efficiency of
alternator and that is needed to determine actual HP needed to drive the
alternator.

The figure Balmar quote is 1HP per 25A output at 14V. Others quote even
higher loses.

For original poster, this link should provide much of what you need:

http://www.balmar.net/PDF/Alternator...or%20Guide.pdf

For a 3/8" belt drive, they don't recommend more than 75A. I would not
exceed this unless you want a lot of belt problems and the need for a
complex system to switch out alternator when you need engine power.
Personally, I would stay with the 55A unit.

GBM