Raising transom

[LDUBS]

Definitely not epoxying transom the the hull skin. No sir, there was no inner aluminum skins in the transom wood. Just the hull. My thinking is that if I bond 14-16 gauge aluminum to either side of the new transom wood, it will help distribute the load more evenly and prevent clamps, rivets, ect from opening the wood to moisture. The may be a 25 HP hanging off of it in the future.

I see your thinking here. I wonder if structural gains from encapsulating both sides is significant. Added weight would be pretty low. In my mind, like @thill says, adhering a skin to the inner (forward) side of the wood transom is good. I may be missing a significant benefit to adhering aluminum sheet to the back (transom) side too. I would do it if I wanted to. No one ever went wrong from overbuilding a transom!

 

[LaqueRatt]

IMO you're over-thinking this. Just slap some plywood in there and put some sort of coating on it. Even paint, especially oil paint will do the trick. Do you want to spend your time enjoying the boat or working on it? If it's the latter I get it, but the KISS rule still applies.

 

[thill]

Definitely not epoxying transom the the hull skin. No sir, there was no inner aluminum skins in the transom wood. Just the hull. My thinking is that if I bond 14-16 gauge aluminum to either side of the new transom wood, it will help distribute the load more evenly and prevent clamps, rivets, ect from opening the wood to moisture. The may be a 25 HP hanging off of it in the future.

I definitely think adding an inner skin is a good idea. Then slather a bunch of silicone across the top and press your transom cap down into it and secure. That will protect the top plywood edge from water and add some rigidity.

Hurry up and get your boat done. Spring is coming!

 

[Ghostryder65]

I definitely think adding an inner skin is a good idea. Then slather a bunch of silicone across the top and press your transom cap down into it and secure. That will protect the top plywood edge from water and add some rigidity.

Hurry up and get your boat done. Spring is coming!

I'm not really a fan of silicone. It has its its uses though. The top of the transom as well as all cut edges and holes will be soaked in thinned epoxy. Then a few coats of regular consistency epoxy. I recently had a thought of using strips of old truck inner tubes where wood floor framing sits in the aluminum ribs. Under the transom cap would be good also maybe. My thinking is the rubber would keep the epoxy being rubbed off of the wood from vibration and hull movement, insuring no water get in the wood.

 

[FuzzyGrub]

It looks like you are using a clamp-on motor. If you are not converting to bolt-thru, need some thin plywood for the clamps to "bite" into. Also recommend using some on the back of transom, like a "wear" plate, like what was there on oem transom.

I agree that the transom height should be fine. When looking at new jon boats a few years ago, short shaft transoms were only available on 14' boats or less. If you are going to push HP limits, might want to see if you can mod/change/add the angle braces, such that the tie into the transom at a higher point. Maybe beefing up the corner braces, too.

 

[thill]

I'm not really a fan of silicone. It has its its uses though. The top of the transom as well as all cut edges and holes will be soaked in thinned epoxy. Then a few coats of regular consistency epoxy. I recently had a thought of using strips of old truck inner tubes where wood floor framing sits in the aluminum ribs. Under the transom cap would be good also maybe. My thinking is the rubber would keep the epoxy being rubbed off of the wood from vibration and hull movement, insuring no water get in the wood.

Silicone is good for that application because it is waterproof, shock absorbing, and it can be removed later, if needed. I would not put anything more tenacious in there. EPDM rubber or inner tube might hold water between the layers in the transom, but is a GOOD idea between the wood and the metal ribs. I use strips from a roll of EPDM roofing rubber, as it's easier than inner tube.

You should NOT have so much movement in there that the soaked-in epoxy rubs off!