Abstract: An improved outboard propulsion system for a vessel in which an intake duct having an intake orifice positioned for receiving water. The intake duct includes a curved flow path directing walls curved continuously to provide a 180 degree turn for the water so as to direct the water flowing in an initial direction to a direction opposite the initial direction. An annular duct contiguous with the intake duct at the end of the intake duct is positioned opposite the intake orifice. The annular duct has walls curved continuously to provide a second substantially 180 degree turn to direct water flowing therethrough through a continuous change in direction of substantially 180 degrees such that the water is flowing in a direction approximate that of its initial direction at the intake orifice and substantially opposite the direction to which it entered the annular duct. An impeller discharges into a mixed flow volute.