I am looking for a correlation between hp and rpm. I have a 76 300d 5 cyl inline diesel rated at 72 hp that I would like to use to power a generator requiring 1800 rpm. If the engine is rated at 72 hp at 3600 rpm will it have 36 hp at 1800 rpm? Could I possibly run it at idle and use a pulley to get the speed for the generator? If it idles at 650 rpm would the hp be 12 hp? I think I need about 23 hp to run the generator. I would appreciate any comments or additonal ideas regarding this use.

Thanks, Roger