Specialists often need to be called for repairs on a boat. But the more you can fix yourself, the more money you have left for other necessities. Repairing a transom is probably one of the easiest fixes on a boat because of its accessibility. With the right kinds of tools, good weather conditions and calm seas, you might not even have to take the boat out of the water.
Determine the extent of the damage. If it is just a small hole, you may get away with just boring out the hole, attaching a screen and applying gel coat to the surface. It may be slightly bumpy, but with wear and a good match in gel coat color, it will hardly show after use.
Draw a line where you will make the cut if the damage requires complete repair of the transom. If you do not have to remove the deck, you can sometimes do this from a swim platform in the water. Most likely now though, you will have to pull the boat out of the water and put it up on a dry dock to complete the process.
Cut the top off the transom and remove the wood. Use the removed piece as a pattern to cut a new piece. If the fiberglass is not damaged, replacing rotten wood inside the transom can be another quick way to make repairs that will help your boat last much longer.
Apply a stitchmat or fabmat over the wood if you need to replace the entire transom. Roll out the bubbles. Put fiberglass on top of that and sand the edges.
Check the size against the boat before putting on the finishing touches. Then insert the transom back onto the boat and seal with adhesives.
Sand the glass and attach hardware. Polish to a gleam.