MnFastBoat

I will be installing a new trim tab soon.
Found out today that I will not be able to thru bolt it
Seems there is a flooring between my two tunnels back on the inside transom. Not really into cutting this open since I really do not know whats underneath it

Is there an issue with NOT thru bolting the backing plate?
It will be a Dana Marine Tunnel tab mounted above the transom notch on the center sponson

Sean H

i would have to wonder if just lagging it in would last in a tunnel tab situtation.... i have heard of bolts bending on some tabs and i don't know what that force would do to lags or screws....

tcelano

I'd recommend definitely finding a way to through-bolt it. Trim planes can generate thousands of pounds of lift, and produce tremendous moments on your transom especially on re-entry from being airborne. Even if all you can get in there are pieces of barstock to back it, it would be worthwhile to cut in and install a 4 or 6" screw-in porthole cover. The good ones, like Beckson, are O-ringed and will be watertight when re-covered. I would not depend of lag screws; the constant cycling loads will work those loose enough to first allow water to get in and soak your transom core, then delaminate your transom and finally rip off.

By all means make sure you aren't cutting into a fuel tank or anything. If unsure, contact the MFG and ask or get the arrangement drawings for your model.

Sean H

don't cats only have two sponsons? how can you have a center one....?


just messing with you....

i still vote to find a way to get that thing bolted on, you don't want that thing flappy around at 90 MPH...