You may be lucky and the rot is only a few inches into the wood, that would save a ton of work, make sure you know the entire transom is weak before you jump in, you can patch from the inside also.

Audio,
One question, does polyester gelcoat stick to vinylester? My jobs have been filling in cutouts to change drives, gelcoating is sometimes required.
Gary

All very valid advice by Audio ... can't you just tell when someone is speaking from experience

I've never used vinylester resin before so I can't speak to it's attributes but it sounds like a good go between from polyester to epoxy.

Gary .. I do know that you can use all the epoxy over polyester you want but not the other way around .. interesting question about polyester over vinylester.
I look forward to learning more !

S

Audio,

Thanks a TON! Lets say that the rot is all the way to the hull sides, will the paste and tabbing to the hullsides be strong enough? Also, how do you get the new wood to adhere to the outer skin of glass/gel? Do you simply paint the old glass and wood with resin or do you lay down mat on the wood first? I tried calling, but had a problem getting through.

See the nastiness...

Here are some pictures from when I did mine. I used Epoxy, and yes, it was expensive.

This was the old transom with a huge hole for the Volvo drive before I removed the wood from the transom.

I did as Audiofn did and cust the fiberglass all the way around then slowly chipped all of the wood with a hammer and wood chisels...

With the wood transom removed, I sanded the inside of the transom glass for a flat and rough surface. Then feathered the transom assy hole about 3-4" back. I took a flat piece of Birch 3/4" ply, covered it with glossy formica, waxed it then scewed it to the outside of the transom. After that I proceeded to start laying glass to cover the holes in the transom..

Once that was completed, I cut two pieces of 3/4" marine plywood to fit. Originally, the Donzi transom just fit inside of the stringers. I cut the new ply slightly larger and interlocked the new transom with the old stringers. I cut the old fiberglass off of the old stringers in the engine compartment and cut out some minor rot where the engines mounted. I cut two new 3/4" ply stringers and doubled up on the old stringers with the new wood. Filled in small gaps with epoxy paste made from west system HD filler (forgot the name). Sanded all rough edges and glassed in.

Minor cleanup and some Interlux 2-part white paint and ready for the Bravo and real power....

Kent, It looks like you made the transom thicker where the repair is. What is the purpose?

Transom is same thickness as original with maybe an extra layer of glass. Picture of the original is misleading.