15 ft jet boat wont trim?

i have a boston whaler rage with the 175 mercruiser engine in it and even if i put the tab all the way down the boat still beats up and down. is there a way to fix that?15 ft jet boat wont trim?
The reason it has a built in trim in the last 20" on the bottom. It's mandatory of all boats 16' and under so no mater how much power it will not trim up for speed it will porpoise up and down. To fix it the back half of the hull bottom has to be fiberglassed flat. Then it will trim up and run smooth.But will be hard to steer.Trim tabs might help in your case.15 ft jet boat wont trim?
get a hydrofoil for it.

carolina skiff