The Rot Doctor


Subject: Dancing Transom
Date: Thu, 25 Feb 1999

Dear Dr. Rot.,

I've got an older 19' Mako in which I have done quite a bit of restoration work. The transom, however, seems to be fatigued in that it has a good amount of flex to it. The test holes I have drilled show no wet or rotton wood that I can see, and 'sounding' it doesn't seem to indicate any void areas. It just flexes, with the deviation being about 1/2" while jumping up & down on the prop area when the motor is tilted up. Scientific test, no?

Could I drill from the top and inject your epoxy to help reduce the flexing? If so, what hole sizes and at what intervals? Thanks for any direction here, as I would like to avoid or at least delay a complete rebuild if possible.

Mike McB.


Could be that the wood has just shrunk over time and "de-bonded" from the glass. If you have drilled and are not turning up water or bad wood then that sounds as if it might be the case.

What I'd suggest is yes, go ahead and drill 4 or 5 holes in the top of the transom and one hole down at the base at the lowest available point. These can be patched later with a little of our Fill-It Epoxy Filler. I would then pour or inject CPES slowly into the holes until it starts to run out the hole in the bottom. Give it about a week or two for the carrier solvents to evaporate away (it'll take this long because of the enclosed space). Close and seal the hole in the bottom.

Next, use our Layup & Laminating Epoxy fill the vacant space in the transom. The L&L Resin is very slow-setting and remains always slightly flexible, even after a full cure, perfect for this application. The CPES will preserve the wood but it is not a filler. The L&L Resin will give you the bulk to stop the 1/2 inch flexing. Give the resin a few days to go solid and then seal the holes in the top. The resin is thick so I'd suggest making the holes as close to 1/2 inch (or larger) as you can.

How much stuff will you need? Well, I'd say a 2-quart unit of the CPES, probably two of the 2-quart units of the L&L Resin, and a 12oz unit of the Fill-It Epoxy Filler. To extend the resin you can mix sawdust in with it, but still keeping pourable. Understand that I'm just guessing about quantities because neither of us can see what's really in there. If the wood is soft it might absorb a lot of CPES, or it might absorb very little. No way to know.

Come back if you have additional questions.