I bought a 2003 Lund Mr. Pike with a 2003 Mercury XR6 motor. I started out with a Tempest 21 pitch prop but went to a tempest 19 pitch to increase rpms. Everyone says the boat should run 50 - 52 mph. I can't seem toget it above 48.5 mph, with a maximum 5400 rpms. A few recommended raising the...