kneeslider74

I had my old cat at the lake and ran it up to 70 or so and it started to porpoise a bit backed it down and it went away. I may have had it trimmed a bit high but not sure. Surface drives.
Is it normal when they start to catch air and go to have this happen?
Can I trim it out?
Or power through it?
Any Suggestions........

GTOFFSHORE

usually at 70 to 80 they do. You can add a trim tab to help but powering through it is what most will do. My old cat was bad about it around 75 hit 80 all gone. I guess it just needed the air up under it.

DollaBill

Nortechs do it at 70 or 80..

WeaponX

Nor Techs can be put up to speed without any porpoise you just have to trim it way in and force the nose down all the way to 75 at full throttle leave it on the dash and trim out.

It took me a long time to get that worked out. It does take alot of power.

Beak Boater

Its ususally only the true tunnel cats that do that. If the cat is made with a center pod they normally will not hop. The cats with center pods usually dont run as fast as a true tunnel will.

4mulafastech

X2

My Talon 22 had a center pod. Smooth running at any speed. True tunnels are a bit more difficult. Just got to play around with the trim, or try and not run at the speeds where it is a problem.

fireboatpilot

Same with my Hydra, I keep the nose down until 70-75 then trim it up. As the speed increases from there I go to WOT.

CcanDo

Set up questions :

1. Location of CG measured from rear notch/step.

2. Drive toe in/toe out amount AND, subject to turning in or out.

3. Prop rake (15, 18 or 21*)

4.4, 5 or 6 blade props.

5. Prop shaft Ht., measured from bottom of sponson

6. Ballast tanks or not. Full or empty....

7. Water pressure....A low hanging water pickup may cause tripping.

8. Going on plane into the wind or down wind...Turning into the wind.

9. Neutral trim to 60 -70, then negative then as it goes through, back to neutral, followed by negative at speed.

10. A straight load of negative may lug the engines and shorten their life. (smaller props and/or lower gears)

CcanDo

A couple more :

1. Tunnel width

2. Tie bar length

3. Transom condition and thickness.

4. Drive model and steering rams

kneeslider74

Well here is what I can tell ya.
4 blade 26p
Kaama surface drives
toe set at 1/2 " toe in
Tie bar set between drives
One step in hull
CG ??????
Twin 500hp
No balast tanks or water pressure gauges
Light winds variable into and into quarter
At even trim starts bucking at 60 to 70
worse on smooth water
True cat
No tab
Think I may give it some toe out and see what that does.
What do you think?