ive resently installed 77 150hp merc out board to my 16 ft carlson challinger tunel with an 8in jack plate my problem is it wont run over 40 mph my rps at wat 5500 this is an on going problem befor i had a 105 chrysler that would only run 40 mph so i changed moters hoping this would give me more go any sugestions would be help full i expeced to run 60 mph at least ????????????????????