I just purchased a 2007 17' Mitzi with a 60 4 stroke Yamaha. The boat is rigged with a 12v 55lb thrust trolling motor, 1 12v battery and 12 gallons of fuel forward. It has a 14" stainless yamaha prop on it and it will only turn over 4800 rpms. The motor was just serviced and has 80 hrs on it. Any ideas as to how I can get the last 1200 rpms out of the boat? If i trim it out it will go to 5100RPM and then cavitate. Any advice will be greatly appreciated.