Jon Boat Project

Sup y'all, a friend of mine has been building a jon boat lately. right now he wants to ask the question of which to use for the rear framing. we've taken the motor off, and the old rivets have been pulled out. there are 2 aluminum sheets that cover up an old rotten wooden board to reinforce the motor. the wooden board seems to be rotting and breaking up, and the top part of the aluminum sheet is cracking(right under the motor mounts) and we want to know if we can just 'cover it up' or do something else. I suggested him to trash the wooden board and both sheets. then reinforce with a thicker aluminum sheet with strong marine foam in between to hold up the motor and help floatation.

whats y;alls opinion on this?

Re: Jon Boat Project

Welcome to iboat.

NO(!!!!!!!!) that board actually keeps the engine from ripping the back of the boat off so if you were to cover it up or use something else this boat would likely have exactly one launch, that wood absolutely has to be there and at least 1 1/2'' thick.

Get a sheet of 3/4 ply and cut out the shape of the transom, use the old board as template if you can, make 2 sheets and glue them together, Gorilla Glue works really well because it is waterproof, soak it with Thompsons water seal then bolt it back into the transom, if it interfered with your new deck work around it since it has to be there.

Redesigning a transom is a really bad idea unless you are are an actual engineer and understand the stresses at work, it is like a pry bar, it is attached at the top and the force is applied at the bottom so evry time you run the boat the engine is trting to rip the transom out of the boat so you have to make sure your transom is strong enough, replace the wood

Re: Jon Boat Project

Just going to second the two layers of 3/4 marine ply (not pressure treated!). It's how I built my 12' and that only has a 6 hp on it. Seal up the whole thing (I did epoxy resin) and you'll be good to go.

Re: Jon Boat Project

I'd suggest sealing the top and sides but not the bottom. I think wood needs to breath, and invariably water will get in somewhere, and needs to drain out.
But replacing a transom board is so easy that if you have to do it every 7 years it's not that big a deal.