2003 mercury 50 hp/ 2stroke/ 3 cyl /elpto/model 1050412ad/ ser. ot728793. pushing a 20 ft pontoon/ with medium load. current prop is a/Solas yc-42-16 . 3311-121-09. OK. the issue is i think i have a spun hub. i can throttle up to maybe 3000/3500 rpm. after that the higher the rpm's the slower i...