i have a 1991 ski boat with a 4.3 Mercruiser, it has a 3 blade 19P prop. I can only go 35 MPH at about 3600 RPM, wondering if i change to a 17P prop, will it help, and if i add the whale tail to the outdrive(or if someone can tell me the correct name for the attactiment, so i dont look like a...