1978 skier boat porpoise

[cbryan70]

I own a 1978 and around 34 depending on the people in the boat it begins to porpoise. it get more intense the longer i hold the speed. Any ideas the shaft and rudder were replaced before i owned the boat

[ski_king]

It can happen depending on the balance of the boat. Mine does it when I have 2 in the back seat and on glass smooth water. If the water has some chopit isn't bad
The boat is designed for sking with the back seat empty.

Short of adding trim tabs that can/will screw up your wake, you will have to live with it.

[WilliM1940]

What follows is pure hear say. I have read other threads from other web sites blaming stringer failure for porpoising in older boats like Ski Supreme, Correct Craft. Oil canning can cause this as the stringers become less rigid. Hope this is not your problem, but may be something to check into.

[SKI*MC]

Our friend has a 77 MC that did the same thing. What he did to fix the problem is he had a little lip installed on the transom of the boat, it fixed the problem, but it droped his top end by about one or two. I would consider adding a lip to the back.