you can beat on a rotten transom with a hammer, and only well after the wood rotted to dust will you hear a hollow sound. Tapping means nothingIt seems to be pretty solid.i went around the whole boat with a hammer and there are a couple small soft spots but the main one was in back where batteries were. it was completely rotton and one motor mount was rotton. Other than that it is solid and transom seems solid.
you are in the denial phase of the 12 step restoration program:After inspecting everything the back of boat is flawless with not one crack in fiberglass. Out drive is solid it does not move at all and bolts are tight. Only the bottom quarter of transom is showing signs of rotton wood. I am thinking about just running it the way it is for awhile, it seems to be early in the rotting process.