Strut-mounted marine propulsion unit

摘要

A marine propulsion unit supported from a vessel by a strut contains an electric motor within a housing and a forward propeller driven by the electric motor and having a diameter larger than that of the housing. Hydrodynamic vanes projecting from the surface of the housing counteract tangential flow generated by the forward propeller. An aft section with a pair of counter-rotating blade rows driven by the electric motor is mounted at the rear of the housing and including a shroud surrounding the aft blade rows. The shroud is spaced from the housing so as to receive the boundary layer of liquid passing along the surface of the housing to inhibit cavitation and improve efficiency. Rearward portions of the shroud are movable to form a clamshell causing a reversal of the flow of the liquid passing through the shroud.