What will trim tabs, ride plate, and place diverter solve?

[diggler]

If anyone can please answer this, I would be very grateful. It's driving me nuts!
I have a 1972 18' Tahiti with a relatively deep V on it.
The pump is a 12JC.
The gas tank has been moved to the back of the boat.
No tabs, diverter, ride plate at all yet.
By myself, the boat porpoises after I get above 45-50mph.
With someone in the front, it won't porpoise until about 60mph.
From 60-65-mph, the boat rides so much out of the water that any wave will cause it to roll onto one side and then bounce back to the other. Kind of like "chine" walking.
At 70-75mph, the boat is almost out of control with porpoising and chine walking.
What would best solve the problem? I mean, it is a fun ride at the high end, but I really don't want to die!

[MikeF]

D, Going through any type of wake is going to make the hull react that way @ speed. When your on flat water and it starts chine walking, that's when realize the hull was not really meant to go these speeds or there are some imperfections on the bottom that are causing the hull to react this way. Does it chine walk on flat water?
It is good that you moved the tank(s) to the back. The porpoise that happens when you're in the boat is where the hull is breaking free from the waters hold. When you have another person up front (same as the fuel tank) it takes more speed to break free from the water.
Most likely it is still a "center of gravity" to thrust issue. The more weight the jet is trying to overcome and finds that it cannot keep only the rear of the boat in the water, it will upset the water drag across the hull and make it move around (bow steer). That is why it feels a little (?!) out of control.
I can't say that I am an expert, but I am trying to give some ideas about the problem you are experiencing.

[diggler]

MikeF:
D, Does it chine walk on flat water?
Actually, it will "chine" walk on flat water also. Cas told me that only about 24" of the boat from the transom is actually touching the water. He said it looks like it's balancing on the keel and just rolls however it feels.
The out of control feeling is still a neat feeling though!

[malcolm]

My Spectra 18 was pretty worthless at the lake. I solved this (sorta) by going to the river. Then I got my Place diverter. I have to run it all the way down in the lake, but it keeps the boat from leaping and porpoising on the waves.
I was talking to a guy on the boat ramp a few weeks ago about his jet with no diverter, but he had tabs. He said he liked the ride better than his last boat with a diverter and no tabs. But, who's to say his new boat wasn't just a better hull.