porpoise active thunder
 

I have mid 90's AT with twin 200 outboards on it. It a fun boat but it porpoise like crazy at about all speed. I have theboat up to about 68-70 if I could keep I under control. The boat runs great with the K-plane flat. But, as son as they come up it starts to porpoise. Then it will Chine walk so bad it will toss you off. It only runs fine with the K-planes.

The Outboards are about 18in off the transom. The lower units are the short shafts. The only thing I can think of is there is just to mush weight ouside the transom. And the props may be to high. If you look down under the hull twards the transom,, the lower unit nose cones tips are about a inch below the botom of the transom.
Some one help, I need this thing to stable out.

You must have the former U2 in Falls Church right?

Can you help me!!!

I am fairly certain that boat was built before current ownership. I'm not even sure Pat (current owner) has even laid eyes on that boat. I also think it's the only one ever with that configuration. IIRC, that boat was raced by Mike Livorsi of http://www.livorsi.com/

I'd suggest a couple things.
1) I think a lot of the items mentioned above here, and also in this thread can help you:
http://www.offshoreonly.com/forums/m...op-repair.html

2) You might give a shout down to Brett at http://www.bblades.com/
He's VERY good at tweaking props and setup recommendations.

I tend to run any boat with the tabs neutral; or at the same plane of the running surface of the hull. This really should not scrub any speed. This could help the hull balance the COG better.

Realize that both of the boats in question here, were purpose built race boats at their time of build. That means they ran with very small amounts of fuel, and 2 people aboard. THAT'S IT.

Now that they are pleasure boats and have changed hands and purpose; things are way different. These boats might have even had ballast tanks in them at one time. And now they are being run with more passengers, tools, parts, anchors, lines, beer, coolers, as well as all the other stuff we take with us when pleasure boating. This really does change EVERYTHING.

Yes, That make perfect sence. There two gas gauges on the port side,,,,,, for ballast tanks,,, I guess?
I only run the K-planes flat with the hull. The boat run like a dream then. It can really handle some ruff water smoothly. I had some 4 blade bravo 26" on it and the problem almost went away. It was about 80% better. I don't think those props had as much rake angle and the MAzco's I also had a big cooler in the front. Thanks for the help.

No porpoise with my 25 at any speed, I run a hydro QIV, think its a 25. It does tend to chine walk at speeds over 60, but it settles with a little tab. Hope to invest in a bravo next summer if I can use it more than 3 times :angry-smiley-038:

No Chine walk at all, here.
How would you know if you have too much bow lift?

Sorry I didn`t get back to you sooner, had to erase your PM`s I can only keep like 3 at a time.
ok so my strakes end 53" before the transom.

What other measurements do you need?

p.s. I have wondered about the fill in piece between the couches.. what holds that up above the floor, I think I`m missing something

Sorry I'm late. I got lost on the way here...

The One Vision Active Thunder really has no porpoise issues unless you are running 30 to 35 mph in perfectly GLASS water. We have played with standoff boxes, "shortie" drives, various props, and probably lots of other stuff that my damaged brain can't remember.
Some of the facts we learned;
My 25 Thunder did not respond well to the standoff box.
We gained maybe 1-1.5 mph, but the boat did not handle well and wanted to launch the nose to the moon in any .kind of rough water. We could slide the box up & down so we played with various drive heights, using various props (Hydromotives & Bravos). We studied a lot of video of our boat as well as the Neville Moberly "Chaos" boat, that aslo had a box. After a LOT of testing, we removed the box and never looked back.

So Gordo, what drive depth do you run for the most efficiant speed without the extension box? In the ruff, the way the boat is set up now, it allways flies pretty level.