The Model 6D continued the designation series of the 1919 Boeing Model 6 but the only similarity was that they are both biplane pusher flying-boats. The 6D was designed in 1928 and 2 aircraft were built between May 1928 and April 1929. The 6Ds rectangular hull was constructed of wood with wood longerons, covered in spruce veneer. The wings were taken from the Model 40 and shortened. The pusher engine and wood propeller was mounted on the lower side of the upper wing.