hi guys. i am new here and to boating period. my dad recently bought a new boat and gave me his old one.. it is a 1974 formula 200 thunderbird. he swapped a 351merc into it a while back. but i took it out today for the first time and it would only do 35ish mph. is that normal for this boat? reason i ask is my buddy has a cuddy 20ft sea ray with a 4cyl volvo and it will do 35mph. not sure what prop is on it, what size and pitch would be good for this boat? thank you in advance guys.. thank you brian.