Abstract: The jet propulsion engine employs a duct modified from a theoretical taper to be enlarged in transverse cross-section along the duct by an amount equal to the area of a cross-section through impellers and stators at any point along the duct. The tube radius at any point r.sub.

Abstract: The gimbal ring nozzle-trim comprises a substantially cylindrical forward control housing mounted to the discharge portion of a marine propulsion device, and having a frustra-orbicularly configured gasket-race flange at its rearwardmost terminal end; an annular gimbal ring mounted to the exterior cylindrical walls of the housing by pins disposed along the horizontal plane cutting the ring and housing distally forward of the gasket-race flange; and a nozzle having a hollow semi-orbicular portion which overrides the gasket-race flange and a substantially cylindrical portion issuing rearwardly from the orbicular portion of the nozzle, the nozzle being mounted by the forward interior surfaces of the orbicular portion to the exterior circumferential face of the gimbal ring by pins disposed through the nozzle into the gimbal ring along the vertical plane cutting the nozzle and gimbal ring.