A convertible golf cart seat assembly is disclosed. The convertible golf cart seat assembly includes a main seat frame attached to the existing golf cart structure, a plastic stationary cargo board supported by the main seat frame, a plastic flip board rotatably hinged to the main seat frame, and a seat with a plastic backer board attached to the flip board. The hinge between the flip board and the main seat frame includes flip board flanges on the flip board and cargo board flanges on the stationary cargo board that abut each other and provide strength to the cargo bed created by the stationary cargo board and the flip board.