Each boat is going to have differing screws/bolts/rivets that in some way enter/traverse the transom. (Especially if POs have done their own thing)
Here is a pic of mine prior to splashwell removal. The pink areas are where screws entered the transom to hold the splashwell in place (they did not pass thru)
The red areas show the bolts that passed through completely...one was for the brace, the other is the tie down u bolts. You will find a variety of bolts/screws/rivets going through form the outside that held transducers, brackets, etc.
Basically if it looks like it enters wood... it must come out. From there you can drill pilot holes and attach lag screws/eyebolts to use as pull points. Or if you are lucky, you might make some progress using a crow bar and getting in from the sides.