Normally you need two layers of 3/4 plywood to fit the transom, a couple of gallons of poly resin, a few yards of medium mat and a few yards of medium weight fg cloth. You will also need some poly putty, acetone and maybe some gelcoat for filling in the cloth weave. As for tools, a grinder with 24 or 36 grit paper, plus an orbital sander with the usual grits of sandpaper, chistel, hammer, sawzall, SS wood screws, clamps, brushes, resin roller and some pressure treated dimensional lumber for stiffening.
Some tips, cut out all the old transom, saving the FG skin if at all possible. wipe everything down with acetone. Sandwich the mat between the two layers of plywood, and clamp and screw it into place. cover the inside with cloth. Remember, you must screw clamp or fasten all the edges of the plywood in place until the resin and glass hardens.
Most of the strength of the transom comes from the 2 layers of plywood, however, you need to glass it in place with enough cloth to give the required strength. An outboard motor with a right-handed prop will stress the top port side of the transom the most.
