Did a Survey & sea trial on a 52' 1987 over the weekend. Rebuilt 8v92's-720 HP with 500 hrs since rebuild. Full of fuel & water, 4 adults on board, 12' of water and marlin tower, which will be removed. At 2150 RPM speed was 21.5 kts, at 2050 rpm 20.5 kts. Does this sound right? Power Boat...