How Do You Fix a Boat Transom?

Your transom should be repaired when damaged or weakened.

When a boat has problems with its transom--the "back wall" of the hull--then the whole boat has problems. The transom is one of the primary load-bearing structures of the hull: it keeps the sides of the hull apart at the stern (the back end) of the boat, it distributes the load from the bow (the front) of the boat along the sides of the boat and it transfers the forces at work on the bow and the sides of the boat to the boat's "backbone", the keel. Transoms can become weak from physical damage, or from wear and tear, including rot.

Things You'll Need

• Grease pencil
• Straightedge
• Reciprocating saw
• Chisel
• Grinder
• Drill
• Hacksaw
• five-gallon plastic bucket
• Mold release spray
• Composite core material
• Utility knife
• Palm sander
• 120-grit sandpaper.
• Marine epoxy adhesive
• Putty knife
• #14 screws, 2-1/2 inches long
• Marine silicone caulk
• Aafety glasses
• Face shields
• Aprons
• Gloves
• Safety shoes

Instructions

1. Draw a vertical line about one inch long with a grease pencil, from the top of the transom, along the inside edge of each side, straight downward on the inside face of the transom. Use a long straightedge to draw a line horizontally between the lower ends of these vertical lines, as if you are preparing to cut off the top of the transom.

2. Cut down along one of the two vertical lines with a reciprocating saw, until you reach the horizontal line which joins the two vertical lines. Turn the reciprocating saw sideways and cut along the horizontal line; you're cutting off the top of the transom. Once you've cut the top of the transom (called the transom cap rail) free, set it aside. You'll need it to finish the repair.

3. Chisel, chip, gouge, grind, saw and dig the flotation material, usually expanded polystyrene foam or balsa wood, from between the two fiberglass panels on the outside and inside of the transom. Remove the stringers--the interior supports that give the transom its rigidity--with a drill and hacksaw. If your transom is weak, the stringers have failed and need replacement. The flotation material needs replacement as well.

4. Inspect the exterior surface of the fiberglass panel that forms the outside surface of the transom for damage. A small crack in the fiberglass is often enough to admit water, and the wood rot that accompanies it, into the interior of the transom. If you find no damage on the exterior of the transom, then the weakness may result from excessive loading--it's worn out from use.

5. Spray the interior of a five-gallon plastic bucket with mold release spray. Mix the composite core material hardener into the composite resin in the bucket, following the manufacturer's directions for the mix. Pour the core material mix into the void between the inner and outer walls of the transom. Follow the manufacturer's recommendation for curing time for the core material.

6. Trim any excess core material from the top or sides of the transom with a utility knife after the core material has cured. Sand the cured core material flat with a palm sander and 120-grit sandpaper.

7. Spread marine epoxy adhesive on the top of the core material with a putty knife. Set the transom cap rail atop the filled transom. Drill holes through the cap rail and into the core material every six inches with a drill. Use #14 screws, 2-1/2 inches long, to secure the cap rail to the top of the transom. Caulk the seam between the transom cap rail and the transom, and the heads of the screws in the transom cap rail with marine silicone caulk that matches the transom color.

Tips & Warnings

• Pourable composite core materials are available at most boat supply houses.

• You will work with a variety of tools, chemicals and materials which may be hazardous to your health and safety. Appropriate precautions and safety equipment, including safety glasses, face shields, aprons, gloves and safety shoes may be required.