My transom was pitted and drilled to death. I thought I might have to replace the whole transom (aluminum and wood). Ended up having a 3/16" thick plate (almost the size of the transom) welded all the way around on the outside and button hole welded at several locations on the inside. Here is a look at the inside of my transom.
Also seen here, he put a 1" x 1" thick walled square tube up under the top lip of the transom that also got welded to the corner gussets to strengthen the transom even more.
Here's a look at the plate he welded to the outside of the transom.
It may not be pretty but it's as water tight as a frogs butt, stronger than any transom I've seen on a boat this size, and the price was right. $40 + a 30 pack of Bud Light for the 3/16th plate, square tubing, and welding. :mrgreen: