Larger deck holes, such as the clearance hole for a vertical windlass, also need to be sealed. Here the technique is to cut back the core around the edge of the opening and then fill that void with epoxy filler. A windlass imposes great strain on the deck it is mounted on, and the backing plate is used to distribute those forces over a larger area. That plate can be plywood or metal. If you use plywood, ¾-inch marine plywood works, but remember to give all surfaces several coats of epoxy to seal against any leaks. In some cases, the foredeck around the windlass installation is curved, and a flat plywood baking plate won't bend to follow the curve of the deck. In cases like this, you can laminate a backing plate in place, made of three layers of ¼-inch plywood. The three thinner layers will conform to the deck curvature and, when the epoxy cures, be as strong as a single layer of ¾-inch plywood. Aluminum backing plates are also sometimes used. Just be sure to use sealant between the steel mounting bolts and the aluminum plates, or corrosion will take place.

Obviously, a liberal amount of sealant should be applied to seal the deck against leaks. I like to use a polysulfide sealant, such as 3M101. You can use 3M5200, but expect problems if you have to remove the windlass for servicing. Avoid over-tightening the mounting bolts and squeezing out all the sealant. In fact, I usually place rubber washers under all my deck-mounted hardware when bedding them. The rubber washer ensures an effective layer of sealant is in place when the fasteners are tightened. You can go back after the sealant has cured and retighten the mounting nuts for a more effective seal.

While you are working on the windlass, you may as well inspect your ground tackle and all other elements of the system. Give careful consideration to the anchor platform on the bow. It needs to be substantial enough to hold the weight of the anchor(s) in a blow, keeping them firmly away from the hull to prevent damage. There also should be some provision for locking the anchor shank in place; don't depend on the pull of the windlass. You will also need to provide a "chain stopper" to lock the chain in place after the anchor is deployed. This is required to take the load off of the windlass, which is not designed to hold the chain in place while anchored.