Hopefully your engine manufacture specified the max prop U can install without over proping the boat & over torqueing your motor. If they don't list it, I would call 'em so U don't get into warranty issues with a new engine. Just curious, how many & what type of batteries does it require, & maybe U can give us a progress report on the output & how long the batteries last before running out? I'm also wondering how much U paid for the motor? I guess this is the wave of the future. Good Luck.