To replace a boat floor, remove all items on the floor, take out the old floor, and use it to cut plywood for the replacement flooring. Coat the new floor pieces with epoxy, and attach them in place. Place fiberglass mat on the plywood, seal it, and lay a floor covering. Finally, replace the items on the deck of the boat.
Begin replacing the boat floor by removing attached items, consoles and seats from the floor. Also, undo any electrical connections. Then, remove the old floor of the boat by leaving a trim measuring 3 inches along the boat's sides. When removing, ensure that the old floor remains intact to the extent possible.
Use the pieces of the old flooring as a template to cut plywood for the new flooring using a circular saw. Soak the plywood pieces in epoxy, allow the coating to dry, and mark the position of the screw holes on the pieces appropriately using the old floor pieces. Drill holes at the markings made using a power drill, and insert screws through them to attach the pieces to the boat.
After affixing the boat floor, cover it using fiberglass mat. Layer fiberglass resin on the mat to seal it, allow the resin to dry, and sand the rough edges using a soft sander.
Make holes for screws in the fiberglass mat, and install a carpet or any other floor covering. Finally, replace the boat's consoles, attached items, seats and electrical connections.