Thanks for all the information as currently I'm trying to find a 15 X 15P enertia to try as Ken from propgods suggested no more than that at this time. What was interesting he said I was only getting 5% prop slip and he seems to like the enertia props also.My friend has a power tech 15.25 X 17 on the same motor and same length boat but different manufacturer and he is 5200 rpm at 46-47 MPH which to me is too low of RPM.