The Rot Doctor


Subject: Outboard Bracket
Date: Thu, 24 Oct 2002

Hi Doc,

I am installing an outboard motor bracket on my new boat. My question is? There will be several holes drilled into the transom for the bracket mounting, plus larger holes for the controls, steering, fuel, etc for the engine.

I would like to treat these holes to protect the the layers of plywood prior to installing the bolts. Any suggestions for treating the wood before anything is mounted to keep out moisture down the road.

Thank you



After you drill the holes, treat the exposed wood thoroughly with CPES (Clear Penetrating Epoxy Sealer). Dab it on the wood and allow the wood to absorb all that it will. Our smallest unit of CPES, the 2-pint unit should be sufficient. The CPES will coat all wood fibers with epoxy resin. The wood will not rot in the future. If you wanted to be obsessive about it, you could wait a few days and then come back and re-coat the wood surfaces with our Layup & Laminating Resin to totally seal it off. All our testing, however, shows that wood treated with CPES alone will not rot.

If there are mounting brackets that are tight-fastened, we suggest using a 100% polyurethane sealant, such as 3M™ 4200, to seal the enclosure. Ideally, you apply the 3M™ 4200, then screw the bracket down to about 80%, allow a few days to pass, and then screw the bracket down the remaining 20%. This in effect creates a gasket that will not leak water.

Hope this is helpful. The application of the CPES is the most important step in protecting your wood. Come on back if you have additional questions.