Abstract: A waterjet propulsion apparatus having a five blade rotor and an eight blade stator that are located within housing sections that define a water flowpath. The housing and hub are designed such that in operation a nonuniform loading arises on the rotor blades whereby greater pressure impinges on the tip area of the rotor blade than at the hub area of the rotor blade. This configuration increases the efficiency of the waterjet while minimizing negative effects of cavitation.

Abstract: A pump-jet type of outboard propulsion unit within a surrounding fluid mem for marine craft or the like, is protectively enclosed within cylindrical shrouding which forms an axial flow passage about the exhaust channel of the propulsion unit through which flow of the fluid medium is induced by rotation of impeller blades. Inflow of the fluid medium to the flow passage is modified at an inlet end of the shrouding by a plurality of angularly spaced vanes attached thereto and extending forwardly therefrom at an angle.

Abstract: The invention features a unique surface configuration which fosters atmosric ventilation and thereby uncomplicatedly reduces drag which is normally associated with implementation of shrouding for a marine impeller. Typical inventive embodiments include a blunt trailing edge and a circumferentially stepped impeller shroud (below the blunt trailing edge), the harmonious union of which affords a generally smooth and unbroken surface which encourages drag-defeating air circulation. During marine navigation, circulation of the air generally describes a path wherein the air first travels linearly downward along the blunt trailing edge, then travels curvingly downward (both clockwise and counterclockwise) along the circumferential step, forming a circumferential air pocket which extends a backward distance increasing in accordance with increasing navigational speed; upon attainment of a threshold navigational speed, the air pocket (virtually) completely surrounds the shroud.