I have a 17' 1985 four winns with a 3.8l omc that has been freshly rebuilt. The boat came with 2 original omc 15 1/2 X 15" props and they worked ok but would wind up to 5000+ so changed to a michigan match 15 1/2 X 15" which actually measures 15 3/4" in diameter, and it was a bit sluggish on...