Porpoising issues

[skeeterman70]

I have a '08 ZX200 with a HPDI 200 that has good holeshot with the 25 T1 prop but the boat wants to porpoise at 3500 rpm's. I am unable to get the boat stabilized unless I speed up over 4000 rpms and the trim all the way down. The prop is approx. 3-3.5 inches below pad. What prop would fix this issue or an engine setting?

[Rodney Bledsoe]

Trim it down.... Look at weight distribution.

[Ranger391v]

As long as you've got the water pressure to do so (and assuming that you're not over-trimmed for the given rpm/speed you're traveling) ..... try jacking the jackplate up.

1/4" at a time .... just make sure you've got enough water pressure each time you adjust. granted you're fixing a low speed issue, but you still need to check WOT, you'd hate to fix one issue and create another.

It wasn't until I hit that magic 1/4" adjustment that my low speed porpoising stopped. 1/4" under where mine is set at right now and it porpoises. Dang'd'est thing I ever seen.

Granted my boat is one size smaller all around than yours, but it's worth a try.

Good Luck !

[Tamale]

What is the best way to raise it? Just tighten that main screw on top a little, and then loosen the ones on the side, then tighten the top screw? Is that all there is too it?

[Ranger391v]

Tamale ..... assuming you've got a Slidemaster or similar design ....

Loosen the 4 side bolts (some brands such as Vance have 6) ...... then turn the center bolt that's located inside the jackplate ....... turn it until you've raised the jackplate 1/4" ........ then tighten the side bolts back down ....... go lake test.