tunnel porpusing?

[hydroViper235]

at what speed can you blow over, my boat starts porpusing at about 60 and i cant seem to push through it. It only porpuses on glass. What do you guys think i need to do. 18' tunnel, 28 big ear on a modded xr4.

[thinback]

I have an old seebold eagle that did the same thing when I first got it.
I had to jack it up about 1 1/2 inches above the bottom. If you still have water pressure go a little higher. I think i'm in the 1 3/4 inch above the bottom now. My boat does'nt like to be kicked under, I had the tendancy to kick it under to cure the hop like a v bottom boat and it doesn't work. The calm water keeps the hull from flying. If your set up is way off you'll never drive thru it.

[hydroViper235]

thanks i'll try that

[rock]

Depends on what 18' boat you have. All of my STVs have had a porpoise. The most recent would bounce pretty good up to about 100 then settle down and run up yo about 130. They can blow over but you damn near have to work at it. Pay attention and be reasonable and it's not an issue. Dixon went over 150 so obviously they can go fast and stay upright. Do a search and you'll find tons of info on tunnels porpoising. They all do it.
Rock

[Carter Powell]

What type of tunnel boat do you have? Many true tunnels will need some setback! A lot of time you just don't have enough air under the tunnel to support the nose of the boat. You don't want too much, just enough to hold it up. You can do this a couple of ways. More setback will allow the boat to get the leverage it needs to balance better and you won't need as much positive trim. You could also add more lift into your prop and let that help hold the nose up if you don't want to go the setback route.

Carter Powell