Bought a 1644 gator trax hunt deck (17.5 feet) with a breakaway plate and a yamaha 70 4stroke on it. Previous owner had a mud motor so this setup is new for the boat. At higher speeds, the boat starts to porpoise uncontrollably unless there's a good amount of weight at the bow. I've included some pics that hopefully show how it's setup good enough. Current prop is a 15 pitch. Don't have a tach, but it seems to run pretty strong through the rpm range until it starts bouncing. Should I raise the motor (only one bolt left) or start screwing with props?

Tried to upload pics, but this site is getting unusable.