How do I Replace a Boat Transom With Seacast?

When your transom gets "soggy"--soft spots develop in the transom's inner or outer walls, it's because the inner supports of the transom, the stanchions, are failing. This means you have to get inside the transom and replace the rotted wood--or it means you can use a pourable material to replace the interior bracing of the transom with a solid transom. Using a pourable material means opening the transom completely, almost major surgery, but it also means a sturdy, stable result.

Things You'll Need

• China marker (grease pencil)
• Reciprocating saw
• Hand saw
• Hammer
• Chisel
• Drill
• Plywood
• Wooden braces
• Mold release spray
• 5-gallon bucket
• Rubber mallet
• Plastic scraper
• Fiberglass cloth, 2 oz.
• Paintbrush
• Marine epoxy resin
• 220-grit sandpaper
• Gel coat repair kit

Instructions

1. Mark the edges of the top cap of the transom with a grease pencil for a line along which to cut with a reciprocating saw. Cut along the line with a reciprocating saw to cut the top cap off of the transom.

2. Use a saw, hammer and chisel, or drill to remove all of the wood between the front and rear fiberglass panels of the transom: stanchions, stringers and braces. Brace the panel of the transom that faces the inside of the boat (the inside panel of the transom) with a sheet of plywood. Cut it to fit between the sides of the boat and fit flush against the the transom wall, bracing the plywood with wooden braces to stabilize the wall of the transom.

3. Spray mold release spray on the outside of the transom walls to ease the removal of overflow that might get on the transom. Mix the Seacast in a five-gallon bucket--more than one may be necessary--with a drill and a mixer attachment. Pour the Seacast into the void in the transom. Tap the outside and inside fiberglass surfaces of the transom with a rubber mallet to ensure air bubbles are freed during the curing process.

4. Wait for the Seacast to cure. Remove the bracing from the inner wall of the transom. Scrape any Seacast from the exterior of the transom with a plastic scraper. Seat the transom cap on the top of the transom, using marine epoxy putty to reattach the edges of the cap to the edges of the transom.

5. Lay a strip of 2 oz. fiberglass cloth along the joint between the top cap of the transom and the wall of the transom and work the fiberglass into the putty with a putty knife. Apply marine epoxy resin to the fiberglass with a paintbrush. Apply another strip of 2 oz. fiberglass cloth, working the cloth into the resin as before. Apply an additional layer of marine epoxy resin.

6. Wait for the resin to cure completely then sand the resin with 220-grit sandpaper until the fiberglass is flush with the surface. Allow the resin to cure and finish by applying gel coat, according to the manufacturer's instructions.

References

• Seacast Transom Repair: Mixing and Pouring