15" prop is sweet, runs great. If I get more than 2 people on the boat I got to throw the 13" back on for more planing power. Still can't break the 30 MPH mark. I got her up to 29 once coming down stream during high flow lol. Usually tops out at 27. But the big difference is I can cruise 25/26 at 1/2 - 3/4 throttle compared to 19/20 with the 13".