I also have no experiences with the Vision so these comments are general. Boats often porpoise because there too much weight in the rear. This means that your center of gravity is too far back. Your engine is heavier than the boat was designed for, and the set back compounds the issue. With that power and that prop, your rig should obtain 112 km easily.

What I would try:
Prop-shaft 1 to 2 inches below pad.
23 or 24 inch 'ski' prop (this will carry you faster than your are going now). Go back to the chopper after issues are fixed.
Three- 20 lb. sand bags in front of feet. (Sand bags because they are easily moved.)
Make sure the boat is well balanced side to side also.

Best of luck! The fun is in the testing!

Welcome! Sweet looking boat. I personally don't have any experience with a Vision but a few guy here do. Hopefully they will chime in.

[ Post made via Android ]

Hello everyone, I recently purchased an 88 vision. I'm having issues with the boat proposing, it has a 150 merc on it which seems to sized right and not over kill. Once I hit over 45 km an hour it starts bouncing. I got it up to 81 km but it's bucking pretty hard on flat water. It has a 26 pitch chopper prop and a full tank and trimmed right down.

[ Post made via Android ]