Abstract: Illustrative marine propulsion systems are disclosed. In a non-limiting, illustrative embodiment, a marine propulsion system includes a pump housing that is configured to be disposed below a waterline of a marine vessel and a centrifugal pump assembly that is disposed in the pump housing. The centrifugal pump assembly includes an inlet pump stage configured to receive inlet water and to discharge impulse water. The centrifugal pump assembly also includes an outlet pump stage that includes an impulse turbine wheel configured to rotate about an axis responsive to the impulse water and an outlet pump stage impeller integral with the impulse turbine wheel. The outlet pump stage impeller is configured to rotate about the axis.

Abstract: A marine vessel air induction system introduces air into an under-hull cavity bounded by an underside, first and second sides, and fore and aft planing surfaces. An air inlet receives ambient air. A plenum receives air from the inlet. A fore planing surface has a trailing edge. The trailing edge and the plenum define a step that communicates with the plenum to generate a first pressure that is less than ambient pressure as a free stream of water moves past the step. Air communicated from the plenum is entrainable in the water. A mixing chamber communicates with the step, and the step and the mixing chamber cooperate to permit kinetic energy of the water to increase pressure of entrained air. At an aft end of the mixing chamber, the entrained air exerts a second pressure that is greater than ambient. Air is exhausted upwardly into the cavity.