The transom itself is just fiberglass, as the rest of the boat, no wood core was used. However, the rudder area has a piece of wood about 10 inches wide running from the top to the bottom of transom. There is wood also glued to the inside of the area above the cockpit seat wall as sunbird said, to reinforce that area for outboard mounting. I know this because the previous owner installed an inspection port on the rear most cockpit seat. Be careful grinding into the gel coat, the overall fiberglass is not very thick. Good luck, west marine has good advice, I also used you tube for info.