Rot Doctor


Subject: wet transom on a fiberglass boat…
Date: Wed, 08 Apr 1998

Hi. What would you suggest for a wet transom on a fiberglass 23′ 1984 sterndrive Wellcraft? (There is wood in the middle of the transom of course.) It seems quite strong with no soft spots, but, when drilling a hole through it, there is some definite moist spots on the drill bit. I suspect that the holes for the bolts that hold the stainless swim platform struts up have let water in. Given that the boat sits in the water 6 months/year, what kind of life should be expected if nothing is done, other than to RTV the strut areas? Can transoms even be replaced on boats like that?



Well, you’re in the beginning stages of what might eventually become full transom wood rot. How long this will take depends on a lot of things, including air temperature and exposure of the wood to air/moisture. I don’t know, but I’d guess that you’re located in one of the cooler sections of the US or your transom would have been rotted out a long time ago.

At this point I don’t think I’d mess too much with what is not yet a critical situation. Sure, the transom can be replaced, but it means tearing off the inside or outside glass laminate and then inserting new wood. Big job! What I’d suggest instead is sometime this summer when the weather is dry pull some fastenings/bolts near the top of the transom (and further down too, if you have access), give it a few says to let the air circulate, and then pour in some of our Clear Penetrating Epoxy Sealer (CPES). This stuff is about the consistency of diesel fuel and will penetrate into dry or slightly damp wood, the solvents evaporate away (give it a week), and the wood will be saturated with epoxy resin. It won’t rot where the epoxy goes.

This is a kind of haphazard approach because you can’t see where the epoxy is going, but on the other hand it will give you some protection (maybe a lot!) and won’t cost a bunch of money. Put in as much CPES as the wood will easily accept. I’d also recommend that you re-seal the fastening/bolt holes with 3-M 5200 or 4200, a polyurethane adhesive/sealant — it’s far better than silicone and will bond with epoxy.

After this, just keep your eye on things. If the wood really rots, you’ll start to see the transom flex. But considering the boat is as old as it is and the transom is still intact, the CPES may just what you need to keep things going.

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