Abstract: The present invention provides a molded boat hull with a novel structural stiffening system. The boat hull has a number of laterally positioned compartments molded into the inner shell with vertical partitions that are integrally welded to the outer shell and are interconnected to each other and to the transom. A keel plate and a transom support are molded into the transom, the inner wall, and a bridge along the longitudinal center line of the boat. A keel support beam is placed along the keel, connected to the keel plate, and adhered into a channel in the boat hull inner shell. A pair of stringer braces is assembled between the integral stringers to provide transverse stiffness of the boat hull.