repairing transom on ebbtide

[hunley1864]

I own a 1983 ebbtide dyna-trak 162 witha 115hp johnson.Right know my transom is ok, some rotting is present in small area around motor mounts about the size of a basketball. I can take the butt end of a screwdriver and thump it on the transom surface and can here different sounds tapping on surface, near the motor mount.I know i am going to eventally have to fix it. has anybody had experience with fixing this problem on a model and year such as mine,people keep talking about removing the transom plate to get to the rotting wood.mine is solid fiberglass on the top motor rail