man that motor should turn a 28b1 and yes you have to saw the steering, but you not be getting chinewalk at that speed with add on steering and if its full hyd steering to the dash that makes no sense sorry to hear this. maybe at the end of the season if its still messed up pull the motor and have it dynoed it should be 545 to 560hp. right now it sounds like your over trimming to get to 70 which causes the walk. after you get it figured out a short will help more for the four blade. and add full hyd steering to the helm if you still have cables going up there. once set up that should be a 80mph boat. ART