I have a 1989 Johnson 88 spl on a 1989 bumble bee 15` 4" bass boat. the motor runs fine, no problems. new fuel system, new water pump,and the compression checks at 117 lbs per cylinder. the problem is it won`t come out of the hole unless I send my son to the front of the boat to hold the nose down. once it planes off it runs fine except it will only run 4300 rpm max. if I trim the nose up the rpm will increase but it starts to porpus. the owner before me put a 12.5 X 21 4 blade stainless prop on and I think this is why I can`t get max rpm. what do you think?