I have the transom epoxyed in two 3/4 inch marine ply two coats of thin epoxy painted on first ..... a 7 oz layer of glass between the back of the boat and the first transom board .. then another 7 oz between the next board. I used milled filler aorund the edges and so far have one layer of 10 oz glass going 6 inches up the transom and 6 inches yo the sides and bottom. It really is hard to detrmine what the manufacture had used I am thinking another layer of 10 oz .. Thoughts ?? 150 hp