I just bought a 99 22' Daytona with Merc 575SCI with bravo one high performance drive that has the low water pickups. It porpoises a lot once it gets over about 70mph.

Does it need tunnel tabs? Where do I get them? How big and in what relation to the hull do they get mounted.

Thanks

-Ryan

Does it need

You may want to check your drive height, it could be set up for a Blackhawk.

What should te drive height be at? The drive is mounted almost touching the rubrail......

That sounds like mine, I fought with it for several years, I was told by the dealer to just drive through it, didn't work. Dave Hargrove ( The dealer, North Coast Marine )even drove over from Ohio just to show me how to run it. He almost flipped it, couldn't drive through it. Tried the tunnel tabs, there was a better chance of stuffing it than stopping the porpoise. Thousands of dollars later I traded it in on a DBC. I was told later that Eliminator set up a bunch of them for the Blackhawks but they were failing so they just put Bravo's on. I was told they all had the porpoise problem. There is a chance a drive spacer would cure the problem, that's the only thing I didn't try, I was told by the dealer it wouldn't work.

I had a 1998 22 daytona and it ran 110. It would porpoise at about 80 but if you drove through it, it was fine. I think they all did that at about 75-80. You dont have enough horsepower to drive through it though....

Mine ran over 100, on a good day it just jumped up and down about a foot, normal day the bow would bounce up and down about 3 feet, bad day you were looking at the water then the sun. I was told to put some weight in the bow, I gave up at 300 lb, it didn't work. I had the boat for 3 years, I was never able to drive through it. bobsbillets, do you remember what the distance was between your rub rail and drive ? that may be the difference.

Try a shorter gear case. There will be less leverage on the hull.

I want to try a -2" gearcase, but don't exactly want to spend 4K+ to test one out and see if it works.


More info:
99 22' Daytona
575 SCI
x-dimension is 6" below bottom center pod\
Brave one with factory low water pickup
1.5 ratio
30p bravo one 4-blade

Best speed thus far was with some positive trim in 9-12" chop. 5100 RPM and 84MPH. Thats 13% slip!

find a used case with no gears. check on this site or buy one with no gears.

Porpoise is usually caused by the hul starting to pack air then unloads the air to quickly so sometimes drive height works. Which is why changing to shorter lowers help. Also more hp drives the front end up keeping it from porpoising ie driving thru it. Don't know ifnthis is making sence but the object is to keep the attitude of the boat up and allowing it to pack air. Trying props with a lot of rake make help drive the bow up without triming it to death.Remeber at 75-80 it is just starting to truly pack air. A lot of times you can see a big diffence if you point it into the wind and waves will make it pack more taking away the air packing problem.