damn if you did the transom suprised no one told you to raise the x dimension at least an inch, or 6 knowing formulas lol

I think you just have a 54mph boat with that hull/engine combination.

The boat ran 54mph with a fresh transom, but all original 1979. Aluminum prop and all.I then rebuilt the drive, took it out and broke 4 pistons. The build is a stock bottom end with flat top teflon coated speed pro pistons, Vortec 906 heads, a comp 262 Xtreme marine flat cam, an Edelbrock air gap intake with an Edelbrock 1409 carb. The exhaust is a GLM setup with 3 inch spacers all exiting through Hardin slash tips. The boat still only goes 54, it gets there a whole bunch faster, but still 54.

Sprink says his 78 F18 did 65 with a 302 back in the day. That is where my crazy idea came from.

What RPM's do you turn?

at 54mph i can be anywhere from 4600rpm to 5500, i am scared to push the rpms higher. Even at 4600rpm and 54mph I am running 19% slip. Every prop I try gives my high slip.

Prop technology has changed a bunch in 35 years. Back then, you had to run the drives deep.

As in to get any bow lift with old props you needed a deep drive, but now we have bow lifting props. Is that kinda right?

I will say that when i am running "fast" I have to have a tiny bit of tab in it or it jumps out of the water. And also the spray comes out the side about 2 ft from the back of the boat.

Any idea on your compression ratio ? not picking on your build but it sounds like you might be running out of HP and just over trimming to get RPM.