Rot Doctor


Subject: Transom Repair
Date: Wed, 24 Feb 1999

I am going to attempt a transom repair. Neither my boy or myself have ever worked with fiberglass. However, I am always interested in tackling a new project if I can get some expert advice. With this in mind, I could definitely use some pointers on the technique and the materials needed.

Transom: no visible rotting showing but it is getting increasingly less rigid and one of the motor tightening screw recently punctured the gel coat. The motor is attached to the transom with 4 permanent bolts in addition to two tightening screws It definitely needs repair and I would like to replace vs fix.

Boat: 15′ 1973 Kenner glass skibarge with a 1973 850 Merc outboard. The boat has a metal channel going around the entire boat and over the top of the transom. From this I deduce that the boat was molded in two parts, and this channel, which is screwed together every 12″, hold the two parts together. The top section has some seats and console sections molded into it, i.e. to remove the seats you would have to remove the top section of the boat. This presents a problem because the seats appear to be attached somehow to the inside floor of the boat, not just sitting on the floor. There is also a splash panel sloping down from the back seats partition impacting the transom approximately 12″ – 14″ from the top. This splash panel also seems to be attached to the top part of the boat.

Repair: Two local fiber glass repair shops quoted me $900 – $1200 over the phone but neither saw the boat. They both said however, that they would have to remove the top part of the boat before repairing the transom.

Thanks for your offer of help on your web page.



Yup, the old problem of the repairs probably being worth as much as the boat. And you can be sure they’d be higher once the yard got into it.

Well, if you want to repair it yourself, here’s what I’d suggest:

If the transom seems to be getting weaker you can assume the inside is rotten. I almost can guarantee it. Pull the motor bolts (you’re gonna have to anyway) and poke around with something sharp and I’ll bet you come up with bad wood. Anyway, you’re going to have to get the top off the transom. I’d suggest cutting the section of metal channeling which runs across the transom (you can screw it back later). Now, if there is another fiberglass covering then get a sawzall and take the top of that off as well. Save it because you can replace it later.

At this point you should have access to the inside of the transom from the top. Assuming so, hook out all the wood you can (get a piece of bent re-bar or whatever and just pull out the wood). If there’s any wood left inside, allow it to dry, or dry it using heater-blowers. Now, soak the remaining wood with our penetrating epoxy (CPES). Just pour it in there until the wood is soaked and then let the carrier solvents evaporate away and the epoxy cure. This may take a week, or even longer if there is a lot of wood left. When you can’t smell the solvents you’re ready to proceed.

Go get some wood such as exterior ply or whatever that is close to the same thickness as the transom width. Cut it to fit as close as possible. Give it a good coating of CPES, especially the edges. Drop it in place. Next use our Layup & Laminating Resin mixed with a little sawdust to extend it and pour that into the cavity on top of the wood and around the wood. Our resin is very slow setting so it will have time to sink down and around the wood. Fill it up as close to the top as possible (you did mask off those motor holes, right?). Allow it to cure (24 hours). Finish off the top with some of our Fill-It Epoxy Filler. All of these components will bond with each other to produce a strong structure. Now replace the glass top (if any, with the Fill-It Epoxy Filler) and the metal channel. You can screw the channel into place, but first drill pilot holes a bit smaller than the screws. Now, re-drill the motor mount holes, mount the motor, and you’re done.

Kind of a prolonged job but not too bad. You can figure you’ll spend about $300.00 on supplies, and you’ll have a super-strong transom.

If you go ahead with this, do the take-apart work first and then get back to me and tell me what you’re seeing and how much bad wood is coming out. I can then give you some guidance on what to buy and how much you’ll probably need.

Good luck to you!