A boat transom and method of constructing same utilizing the outer skin of the hull and transom while still in the hull mold. A bulkhead is disposed in forwardly spaced relation to the outer skin of the transom and the space therebetween is filled with high tensile strength synthetic resin which may be of the polyester type blended with a suitable hardener. The resin includes entrained microspheres evenly dispersed throughout the transom body and ground fiberglass reinforced plastic scrap. The transom body is cast in a series of merging layers containing fiberglass reinforcing which extends in zig zag fashion from edge to edge of the transom body cavity and additional strands which extend in a skewed pattern. The bulkhead may be removed after the casting operation or may be allowed to remain in place. A further aspect of the invention involves the casting of a fiberglass reinforced synthetic resin transom body in a generally horizontal mold, or an upright mold, separate from the hull mold.