Boat engine covers must be movable or removable. Covers for inboard motors are flush with the deck of the boat and hinged to provide access to the engine. Outboard engines are manufactured with a latched case cover that should be protected from the elements when the boat is not in use. Covers for inboard motors are made with fibreglass and mounted with stainless steel hinges. Covers for outboard motors are made with marine vinyl fabric and stored away when you're on the water.
Measure the size of the opening in the deck above the engine. Deduct one inch from the width and length and cut a piece of 5/8-inch plywood to this size as a platform for the fibreglass cover. Refer to the instructions on the fibreglass kit and apply resin and fibreglass cloth to one surface and the edges of the plywood. Allow the fibreglass to harden completely.
Turn the cover over and sand the rough edges of the fibreglass with a belt sander and medium grit sandpaper. Turn the cover upright and touch up the surface with the belt sander for a uniform finish.
Mark the midpoint of one of the long edges. Drill a one-inch diameter hole two inches from the edge at the midpoint and attach a flush ring pull to the cover. Position two hinges on the opposite edge of the cover with the hinge pins aligned with the outside of the edge. The hinges should be two inches from each end.
Use the pre-drilled holes in each hinge as a guide and drill 3/8-inch pilot holes for bolts. Insert 3/8-inch stainless steel bolts in each hole. Put large flat washers and nylon locknuts on the underside of each bolt and tighten the nuts with a box wrench.
Place the engine cover in the opening on the deck. Drill pilot holes for the opposite side of the hinges and attach the hinges to the deck with stainless steel bolts, flat washers and nylon locknuts. Lift the cover with the ring pull.
Make a pattern for a vinyl cover using cardboard and scissors. Typical outboard covers have a main section that covers the front, top and back of the case cover. Side pieces match the size and configuration of the case cover and attach to the main section.
Place the cardboard pattern sections on a piece of vinyl marine fabric and cut the sections of the cover. Allow 1/2 inch excess for each seam. Fold the edges of each section along the seams to make 1/4-inch wide double borders.
Tack the sections together with random stitches at several points along the seams. Fit the cover over the outboard motor and mark where any changes are needed. Remove the tack stitches if necessary and adjust the fit of the cover. Stitch the seams permanently with doubled nylon thread.
Refer to the fibreglass instructions regarding primer or sealer for wood applications. Apply non-slip deck coating to flush covers.