When replacing my transom, removing the wood was a chore. Used a chain saw for some. Welded a old wood chisel on the end of a 5/8 steel rod long enough to reach the bottom of the cavity and welded a T handle on the other end. Worked great to separate the wood from the skins and break up the rotted wood. But the best tool I found was my pressure washer. Using a jet tip it blasted the old wood out and left the cavity void of any wood.
