Plywood boats have the advantage of being light and easily manoeuvrable, but the plywood is prone to rotting and deterioration. The layer of plywood is covered in an epoxy or laminate to make the boat as waterproof as possible. With time and wear, the protective layer can come off and damage the plywood below. Plywood may also begin to rot from the inside, especially when kept in a moist, humid environment. Plywood boat repairs can be accomplished using supplies and tools from home improvement stores.
Determine what parts of the boat need to be repaired. If there are many areas that are rotted or deteriorating, you may wish to replace an entire panel of plywood on the boat instead of making small patch repairs.
Cut away the rotted area(s) using a saw or a router. If you are using a router, set the router to a length that matches the plywood, so that you do not damage the interior structure of the boat. While you should make the cuts from the outside of the boat, you may need to make small cuts around the interior structure from the inside to guide you.
Sand the cut surfaces on the boat, using a rough sandpaper.
Cut a patch of plywood to fit into the hole that you cut from the boat. You may need a measuring tape to obtain an accurate fit. Sand the edges of the patch so that they will hold onto the epoxy when you patch the boat.
Cover the edges of the patch and the edges of the hole, using a marine-grade epoxy. Follow the manufacturer's directions to hold the pieces together while the epoxy sets up.
Apply epoxy to both the inside and outside of the patched areas, following the manufacturer's directions. You may need to apply several coats to match the rest of the boat. If you need to reinforce the patch, you may insert fibreglass or a glass cloth in-between the epoxy layers.
Work in a well-ventilated area and follow manufacturer's directions when working with epoxy.