TACO Marine Project Boat Part 7 – Replacing the Transom

What is a do-it-yourself project without a glitch every now and then. The TACO Marine Project Boat ran into just that – after removing the motors and inspecting the transom, we discovered the transom’s interior plywood core lacked structural integrity and was beyond repair. The solution?

DIY - replacing the transom on a boat

Completely remove the entire transom and replace it: Fiberglass hulls need extra reinforcement and the transom is one of the main areas requiring added strength. Transoms most often consist of layers of plywood, cut to shape and bonded in place with resin, and then apply more layers of fiberglass and resin. With Inboard/Outboard installation, a big hole is cut through the transom, and many times holes are drilled into the transom to mount swim ladders, transducers or other accessories. When the sealant fails around these holes, water begins to leak into the plywood core, causing it to rot and delaminate.

This boat transom needs replacing

Cut, grind and sand: In our project boat, we cut away and ground out the layers of fiberglass, to completely take the transom’s plywood core out. We carefully chiseled off any remaining pieces of plywood bonded to the hull and then sanded with 80-grit sandpaper to make bonding the new transom in place much easier. DIY tip: Use an artist’s foam board material to make a pattern for the new transom. It doesn’t need to be exact, as any little gaps get filled in when the new transom is bonded in place.

replace a rotten transom with composite materialAttaching the new transom: We opted to use Coosa Composites structural panels because they don’t rot, are light weight and they have the structural properties of fiberglass. Coosa Composites materials utilize the latest knitted fiberglass and woven raw materials – making it an excellent replacement for wood and other traditional core marine materials. Next, bond the transom in place using resin and proper fillers.

The next step is to inspect the stringer grid, bulkheads and core materials by removing the deck for a thorough inspection. To see Parts 1-6 of the TACO Marine Project Boat and other helpful DIY tips, click the links in the right column.