When water enters the wood, the “dry rot” process starts and soon you may discover a “spongy” deck or a delaminated transom. Contrary to popular belief, a bead of sealant around the hardware being installed is NOT going to offer enough protection to prevent water penetration.
Step 1. Be sure to use a template to mark the location where you want the holes drilled for the bolts or screws.
Step 2. Select a drill bit that is about ¼ larger than the bolt or screw itself. (I prefer using a wood drill bit.)
Step 3. Carefully drill down through the outer fiberglass skin. Next proceed to drill through the wood coring only. If you were very careful and were able to stop drilling before you went through the inner fiberglass skin, you can skip step # 4; if not proceed with Step 4.
Step 4. If you have drilled the hole all the way through the inner skin (oops), then wrap a small piece of plywood in wax paper and tape it to the inside of the hull to cover the inner opening of the drilled hole you just made. This block of plywood will prevent the epoxy, which you are now going to use, from sagging due to lack of support. Not to worry, The epoxy will not stick to the wax paper and after the epoxy sets up, you’ll remove this block anyway.
Step 5. Fill the drilled hole with epoxy resin mixed with microballoons until it thickens.
A few words of caution: When using any of these two-part epoxy mixes, make sure you are wearing a respirator and there are no open flames around.
Also, be sure to remove any excess epoxy from around the hole and make the surface as smooth as possible. This is important, because once the epoxy cures, it’s as “hard as a rock” and very difficult to sand and smooth out.
Step 6. After the epoxy has dried/cured, drill the correct sized hole for the bolts/screws you are using. Next, liberally apply sealant to the bolt/screw and install it. As you can now see, the hole is surrounded by solid epoxy and sealant and will not leak.
Step 7. If you are installing something that requires a large hole in your deck, like a hatch for instance, I recommend applying at least three (3) coats of clear penetrating epoxy to the raw edges of the coring. A Clear Penetrating Epoxy System is a good choice for this step and will completely seal the coring and prevent water intrusion.
Well, that’s the tried and true way I install any bolts, screws or through hull fittings on my boat. This process takes a little longer and has a few more steps than normal but, it’s worth it in the long run. By doing a little extra at the outset, you have eliminated water invasion into the coring of your hull, the possibility of dry rot and the time consuming/costly process of replacing sections of your boat at a later date.
