I recently purchased a 1988 Bayliner Capri with a 1988 85hp Force. I desperatly need a new prop. The prop I took off of the motor is a 13 1/2Dia. with a 17 pitch, the book calls for a 13 Dia. with a 19 pitch. (both 3 blade) How do I find out which prop is the right prop for me?