Wedges or trim tabs to correct porpoising?

[user 21876]

Have any of y'all been able to correct porpoising with something as simple as a wedge on the bottom of the hull?

Example

My boat is light, battery and fuel up front and still porpoises with my daughter in the front, although she's only 96lbs.

I have a full width trim tab 1" wide on the back, basically the hull extended beyond the transom 1".

I will have to make cuts in the tab to be able to bend just the 6" the engine builder is suggesting. I am hesitant to make those cuts because I have read where it makes push poling the boat backwards a bit of a pain. The engine builder is adamant that 2 6" sections bent just an 1/16" will do wonders, but it could take as much as 3/16" to stop the porpoising.

I am just wanting to be sure before I go cutting slots in a brand new boat.

Thanks Darryle

 

[CedarRiverScooter]

I would attempt to prototype the geometry before committing to it permanently.

Maybe glue some thin plywood on? It wouldn't have to last more than 10 minutes while you evaluate the benefit.

 

[VinTin]

Have you thoroughly exhausted motor trim options?

 

[user 21876]

The motor is designed to run as a surface piercing prop to run shallow water and even in little to no water on mud flats.

In my case it is buried in the water. When I get get close to the surface with it the porpoising starts. This severely cuts into the ability to run shallow, actually eliminates the possibility.

I will use a temporary epoxy to bond the wedges on and if they fix the issue I will fabricate a set and have them welded on.

 

[Zum]

I have the same " 1" trim tab" on my boat (1652 shallow tunnel), I never cut it and was able to bend the whole length( I don't push pole). I fish mostly by myself and when I had a 40hp on it , I couldn't run wide open. I bent the whole tab about 1/8" and it still porpoised a bit but helped enough I could run wide open. I now have a 30hp and straightened the tab level again, no porpoising with the smaller motor.


Sent from my SM-T350 using Tapatalk

 

[Zum]

I have the same " 1" trim tab" on my boat (1652 shallow tunnel), I never cut it and was able to bend the whole length( I don't push pole). I fish mostly by myself and when I had a 40hp on it , I couldn't run wide open. I bent the whole tab about 1/8" and it still porpoised a bit but helped enough I could run wide open. I now have a 30hp and straightened the tab level again, no porpoising with the smaller motor.


Sent from my SM-T350 using Tapatalk

Didn't realize you are using a surface drive, my outboard experience won't be relevant.

Sent from my SM-T350 using Tapatalk