I am new to the boating thing just purchased a 05 sea ray 200 sundeck 4.3 mercruiser 220 hp. the first day out just 2 people on boat with full tank of gas i topped out at 32 mph and at 4000 rpm full throttle. had it out yesterday same thing 2 people 1/4 tank of gas hit 38 mph at 4300 rpm. i know the weigh of the gas but i know the boat should hit over 40 mph either way i have a 19 prop on it now boat has 250 hours on it the place where i bout the boat from told me to put a 17 prop on it but not sure if there is another issue any help would be great thanks