How do I repair a pitted and corroded transom? Large holes?

I removed the wood from the transom for replacement. When i ground off all the grime, corrosion, caulk, ..., I found the aluminum was pitted. Does this pose a problem? Is it a structural issue? If so how do you repair? I also found several of the bolt holes were corroded out. How can I repair them? JB Weld? Have a patch welded on?

Those are some pretty big holes......I would defiantly have them welded up......for the small stuff you could use Marine-tex epoxy, IMO that stuff is better than JB weld. I used it on my transom and it worked well for the pitting and small holes.

If you were not going to weld, here is what I would try. Either prime and paint or seal your wood transom in fiberglass resin. For the smaller holes (and it may work for some of the bigger ones), bolts with washers and marine sealant or silicone should be on the outside and nuts with lock washers on the inside. That will keep your transom secured to the boats nice and tight. For the bigger holes you can try (but I can not guanrantee) to put an aluminum patch over the holes and secure it to the aluminum hull with epoxy or marine goop. Before you put the patch on you may want to use marine goop or epoxy on the wood which is exposed through the hole to sort of seal it in case the patch falls off. The patch should not fall off because the it is on the back of the boat and not on the front. If the patch should fall off, I'm not sure how fast water would enter the boat if the transom is tight against the hull. Goog luck.

That looks nasty. I would make a pattern of the transom and get 2 pcs of aluminum the same thickness as the transom and sandwitch the old transom with them. I would use marne sealant as a glue and use bolts with fender washers to hold it on. You may not have enough metal to weld a patch on the way it is now. If you don't have a lot invested in the boat you may want to change boats as a 2nd option

I agree with the comments above .... get it welded. But I also agree that the existing transom is really really thin and it will be very hard to weld that without blowing it to pieces.

I second the idea of cutting out a new piece (or two) of aluminum and attaching it to the existing transom.

And to throw out one more thought .... it could cost a couple hundred bucks to buy some aluminum and supplies to reinforce your transom yourself .... or closer to 500 to have a fabrication shop do it for you. You could get a good condition used boat similar to your current boat for about the same price. Just something to think about.

Thanks for the thoughts. Really good input. I measured the hull today with calipers and it is .063". Not very thick for welding. The large holes actually have an aluminum brace that goes over them - see the picture. Since they are above the water line, I'm thinking I will put a patch on the backsides, JB Weld them, and then grind them smooth. I'm guessing someone put PT wood on the transom at one time and that caused the pitting. Any reflections on these ideas? Would glassing the inside be better than an aluminum patch?

If you are going to pur a motor on that boat you will need some extra support back there. I would not trust small patches in the transom with all the strain that is put on it. You could lose your motor or worse your or someone elses life. If I covered something like that up with a half a## fix and sold the boat I could not live with myself, But it is yours do as you see fit

My transom was pitted and drilled to death. I thought I might have to replace the whole transom (aluminum and wood). Ended up having a 3/16" thick plate (almost the size of the transom) welded all the way around on the outside and button hole welded at several locations on the inside. Here is a look at the inside of my transom.



Also seen here, he put a 1" x 1" thick walled square tube up under the top lip of the transom that also got welded to the corner gussets to strengthen the transom even more.

Here's a look at the plate he welded to the outside of the transom.



It may not be pretty but it's as water tight as a frogs butt, stronger than any transom I've seen on a boat this size, and the price was right. $40 + a 30 pack of Bud Light for the 3/16th plate, square tubing, and welding. :mrgreen:

JMichael said:

My transom was pitted and drilled to death. I thought I might have to replace the whole transom (aluminum and wood). Ended up having a 3/16" thick plate (almost the size of the transom) welded all the way around on the outside and button hole welded at several locations on the inside. Here is a look at the inside of my transom.

Also seen here, he put a 1" x 1" thick walled square tube up under the top lip of the transom that also got welded to the corner gussets to strengthen the transom even more.

Here's a look at the plate he welded to the outside of the transom.

It may not be pretty but it's as water tight as a frogs butt, stronger than any transom I've seen on a boat this size, and the price was right. $40 + a 30 pack of Bud Light for the 3/16th plate, square tubing, and welding. :mrgreen:

Click to expand...

I love the buddy network.......beer will always get the job done........ =D> =D> :beer: :beer:

That is a great repair .... not the prettiest, but definitely functional and strong. This is a far superior fix to using goo or sealant of some sort.

With all that said though, if you absolutely don't have access to a welder ..... you CAN use JB Weld, 3M5200 or other type sealants in very effective ways. Some creativity can solve a lot of problems.

That'll work. I had a very similar condition on my boat a couple of years ago. I traced the profile of the entire transom onto cardboard and then cut a piece of .063 5052 to match. The hull was also .063. After killing all the corrosion I had a guy weld the new skin right on top of the old before installing a new transom core on the inside. Sealed around the seams with Gluvit on the inside and Steelflex on the outside. Should be good to go another 25 years.

Well based on your encouragement, I decided to have the big holes welded up. I took it to a fab shop and they put a patch behind it and filled the holes. They also repaired the crack at the top edge for $40.

I stopped by West Marine and picked up epoxy for the transom wood. In discussing the need for marine plywood, he said American marine grade has no standards and can have voids and plugs. I've decided to pick up some AC plywood and fill the edge voids with epoxy. He mentioned that if the plywood is exposed to moisture, it won't matter which kind of glue there is because it will still rot. He suggested I use several coats on the faces and 3 coats on the edges. He also suggested I use glass with the epoxy for stiffness.

As mentioned on here and by West, I'm going to pre-drill the holes oversized and fill with epoxy. I can re-drill them afterwards and have the holes sealed also.

I have a busy weekend to get this all finished.

I'm not sure why anyone would waste time elaborating about glue not stopping rot since that's never been the purpose of the glue. The reason for an exterior rating on plywood is because the glue used to bond the layers together does not break down when exposed to moisture. Plywood that isn't exterior rated uses a different glue, and when the wood gets wet the glue won't hold, so the layers will separate. The coating you apply (varnish/epoxy/resin/etc) is to prevent water from getting to the wood as much as possible and that's what prevents/delays any rotting of the wood. In a perfect world, your coating would prevent 100% of the moisture from getting to the wood forever, and if wouldn't mater if you used exterior plywood or not. But I think most are in agreement that this isn't that perfect world. At least not in that respect. :lol:

Thanks for the thoughts. I think what he was saying is that delamination or wood rot doesn't matter. Either one will be a problem. I guess that is my perplexion. I can tell from other post that the best laid plans to seal the wood are no guarantee. I guess you do the best you can and just drop back and punt if several years later it doesn't work. I just want to do it right the first time to keep from having to do it a second.

Thanks for the suggestion of treating the transom metal. I was inclined to coat it with epoxy for protection and sealing. Does the aluminum need to be chemically treated to eradicate the corrosion. I have wire brushed it to the aluminum but the pitted areas still have corrosion in them.

Thanks for the instruction on the 5200. I wasn't sure how much to apply, but I'm guessing I will use it liberally.

When they welded the transom, I didn't like the patch on the inside. Saw another fix on here that looked the same. I guess that is part of it. I think they overheated it some, because it has some warpage. I'm sure the wood will flatten it as much as possible.

if you have access to an oxy - acetylene torch you can braze every single one of those holes shut, strong as original, with aluminum brazing sticks and flux. it's a bit of an art which you can practice on holes on pop cans, but once you get it, its amazing what you can do. Brazing uses lower heat than welding, so it's easier to repair aluminum by brazing.

youtube some videos "brazing aluminum"

I just had a welding shop patch the big holes. I looked at welding them myself, but I have never mig welded on aluminum and I understand it is a big learning curve. I hadn't thought of using the torch. I may try that on some holes that need covering. Just nervous about blowing holes as fast as I patch them.

I have to keep in mind that the project is to enable me to fish, not to get interfered with by my OCD side that says make it perfect.

Bought some BC plywood today and cut out the transom. As mentioned by others and the West Marine rep, I drilled the holes large and plan on plugging them with epoxy and re-drilling them to install. This will help prevent water from getting to the wood from the bolt holes. I'm glad I decided to epoxy and glass the transom boards. The plywood was poorly glued and every time I cut or drilled it flaked the sanded layer off. Hopefully when I finish, no one will be able to tell.