I have a 1992 Invader 18.5 ski boat with a 1996 Johnson 90hp with a 13.5X17 cupped prop. Whenever trying to make a corner while on plane the prop will grab air and the boat will over rev. I've lowered the motor to the last holes and it won't go any lower, still the same result. Also while running near WOT bumping up on the trim has no effect whatsoever, until the motor basically raises too high and blows out. Any thoughts or ideas? Thanks in advance..