question about 15' tunnell

[wawa c]

thanks guys. i raised the motor about 2" thats all icould without drilling new holes in my new transom. splash from the motor going straight up and into the splash well went away. thats good. whats bad is now i get cavitation just as the boat is planing off or when throttle is really jumped on. it acts like a spun hub because even when i back off or feather the throttle it still spins, tried a different prop that was in my garage seemed even worse. the first prop is a stock 131/2 x 17 aluminum i had run this prop on this motor with my 18' aluminum fish boat with no problems, the second prop was given to me with a box of other parts condition unknown. same size and pitch. i know i need something different prop wise, what would you all suggest? heres a side view of the rig.