21ft scarab porpoising
 

Help!!
I have a stock 21 scarab 1 w/a 350 260hp mercrusier,(no trim tabs) I cant get the nose to stop bouncing up and down. I have tried a 19p 3 blade and 17p 4 blade prop, the 4 blade helped a little. What do I do? Its starting to take the fun out of this boat, Its a constant battle w/the trim switch. How do those hydro foils work?
Any advise would be greatly appreciated
Thanks
Paul

does it have trim tabs on it they will help..i had a whale tail on my boat and it slowed it down almost 6mph...

No I dont have trim tabs, I wish it did and silent choice too.
Are trim tabs the only way to eliminate the problem?

I have used the hydrofoils on smaller boats with great success. For the $ 50.00 I'd try one, they do eliminate propoising and actually provide a better plane out ime. I didn't notice a drop in the top speed.

Most hot outboards such as the Allisons use them also.

Thanks for the info.

I had a 22 Scarab, Trim Tabs made a huge difference all round. I would definately look into some Bennett or similar tabs. I ran a 21 3 blade Mirage prop.
Good luck
John

Look for a hook or rocker in the hull near the stern. Might be the cause.

Also, try a Mirage Plus prop, which may carry the bow without losing a "bite" and causing the hop. Alternately, try a Hydromotive that may lift the stern more and smooth out the pogo. You never know till you experiment. Either way, though, I'd steer clear of any "normal" prop, aluminum or stainless - stick with "performance" props with decent amount of rake.

Most times, though, hull profile is the blame for ill mannered porpoising.

Spend the $'s for trim tabs. Will make a huge difference, especially if you boat in area with any type of wind & wave action to contend with. you won't regret it.

tabs are better but will coist you more, I had a friend that put a foil on his 20 baja and it helped out, also it was the only way he was able to get on plane if he had a fully loaded boat.

Check out boatfix.com . In December I bought Lenco 12X12 tabs for $382. Retail is $505. The Lenco tabs are electric, no hydraulics and a snap to install. Each actuator has has an electric motor turning a ball screw arrangement that moves the tabs. Beats running hydraulic hoses, bleeding, watching level etc.