Re: prop recomendation
Calling the manufacturer won't really help, but lakegeorge is correct that you need to get your tach working. That's the surest way to determine whether a given prop is the right one. One can say with certainty the 21 is wrong, most likely over by quite a bit, but the thing about propology is this; you can put the same prop on three identical motors on three identical barges and
not get three identical sets of results. Were I you I'd start the process by getting a 15 pitch prop from a dealer who will take it back if 15 turns out not to be the magic number, then I'd fix the tach and take a test run under conditions most likely to be encountered on a regular basis and compare the max RPMs attained to the max RPMs recommended and go from there. Your motor's specified RPM band will be in the owner's manual and should also be somewhere on the motor. Good luck.
