I recently bought an '84 Grumman 1448 with an Evinrude 25HP outboard. The boat's in excellent condition, except the transom. The transom hull is double walled aluminum with a wood board sandwiched in between. The wood can only be felt at the lower inside corners, and I can tell it is rotten. There is no way to get to this board to replace it without cutting the aluminum away. I don't want to damage the transom strength and don't want to pay someone to heliarc it back together. I'm thinking of adding an aluminum plate, maybe 1/2" thick, to the inside of the transom and through bolting it. Any ideas?

If you're gonna do it; do it right.

The fee should be minimal for tacking it all back together in the end, and you'll have the ease of mind knowing it was done properly, as well as widening your knowledge and bond with your vessel.

Welcome to TinBoats. When you get a chance, share some pics of what you're working with and update you profile with your location. You might have another member that lives close that could help you replace the board, or someone else might be able to guide you better if they see what you're working with.

If you can get all of the old wood out you might be able do a pourable transom.

Pourable transom? What is that and how does it work?

Pouring a transom

viewtopic.php?f=3&t=13354&hilit=pouring+transom

Mine was held in with 4 rivets and 2 small welds about an 1 1/2" long each. The person I brought my boat from had done the same thing to it. It works but is just a patch. The best way is to do it right the first time. Either with wood or aluminum like I'm doing.

I used that when I rebuilt the transom on my Ozark tri-hull. I cut a section out of the top of the transom (fiberglass) and pulled the old rotten wood out. Then I replaced the center with a thick piece of marine plywood, then pour the resin in around it. It soaked into the edges where I removed the wood and around the plywood center. The final fix was very strong, maybe stronger than the original thin wood transom. And the resin won't rot. It was rather expensive so you need to fill as much of the area with wood as possible. The boat shop gave me a price of $700 to make the repair and I did it myself for about $150 in material. I've got a lot more time than money.

What thickness is the inside skin? Most companies add the skin inside to keep water from getting in the transom. Some use it as added strength. You say you can feel the bottom of the wood, does that mean it is all exposed? Could you get the wood removed from there? If not then you will have to take the inside skin off. Once you get there I would just build an aluminum transom out of some aluminum tubing. Something like a 1.5X 3 or 4" Build a square that will allow the motor bolts to go though the aluminum tubing. Maybe add another one in the middle for support and then weld it all up. Then you can either replace the inside skin or not.

The inner skin covers the entire transom, and it returns at the bottom to touch the outer skin, so there is no way to get the wood out without cutting away some or all of either the inner or outer skin. I can feel the rotten wood at the bottom inner corners. I'll show pics tomorrow once I figure out how.

Gotcha! I would remove the inner skin and just build an aluminum tube transom. Then you can just stitch weld the skin back in.