have a 1998 370 sundancer that was repowered from 370 HP to 8.1HO 420 HP Mercruisers by the dealer for the bank. While 3500RPM seems to be the touted as efficient cruise speed for the 370HP it is certainly NOT the case for the 420HP. Any tests results or info on efficient cruise speed as the boat does not have fuel flow meters or are the 420 HP just a fuel burner?
