Seal the Deal
Cutting or drilling is just the start. To finish the job, you must properly bed the fitting with sealant.
Start by cleaning the surface with adhesive remover or acetone. Above the waterline, silicone sealants are often acceptable. For below the waterline, or for additional bonding strength, opt for a urethane-base sealant such as Sikaflex 291 or 3M 5200.
Place a generous bead around a fitting’s flange, so that sealant evenly oozes out around the perimeter of the hole as you push it into place. If additional screws are required to secure the flange, squeeze a bead of that same sealant into each hole before installing them. Inside the hull, run a bead of sealant around the interior of the hole, and then snugly tighten the collar or nut.
Urethane sealants often yellow when exposed to the environment. If Regal needs the strength of a urethane but the clean appearance of silicone, workers may install a fitting with urethane, then overcoat it with silicone. Vahle says, “That’s going to stay white out in the environment.”
Working neat with sealant can be tough. Regal pros share these tips: Use a plastic scraper, or scrap of Formica, to remove most of the excess. Avoid razor blades; it’s too easy to damage the surface. A scrap of foam rubber with soapy water wipes away the final filmy excess better than paper towels do.
If the hole is through cored fiberglass, you’ll need to seal out moisture. Many coring materials don’t readily absorb water. Regal does little more than coat them with gelcoat. Wood cores, however, require added attention.
To properly seal a wood core, use epoxy resin, and brush it onto the exposed surface to thoroughly wet out the exposed end grain of the wood. Allow the epoxy to soak in. Recoat several times. Some pros suggest preheating the area with heat lamps or a heat gun, allowing the resin to penetrate even deeper.
Don’t forget post-project common sense. If you’re drilling through the bottom of your boat, check that it’s watertight before you go offshore. “Drop it in on your trailer and verify there’s no leak,” suggests Vahle.
Yup, boats are chock full of holes. But as we discovered, a few more, when properly drilled and sealed, won’t rock the boat. On the contrary, those holes just may make it possible to add the equipment and features that make your boating experience more enjoyable, convenient and even safer.
So plan ahead, use the right tools, and drill that hole. It’s easy when you know how.