Abstract: A water jet propulsion unit intended for use in jet boats. The unit has an intake section, a pump section and a nozzle section. In the pump section there are two counter-rotating impellers on concentric counter-rotating shafts calibrated so that any radial flow created in the upstream impeller is converted into axial flow by the downstream impeller. In one embodiment the nozzle section has a throttled outlet to allow for a high mass/low pressure operation while maintaining pump priming. There are no support structures or stators downstream of the intake section in the preferred embodiment.

Abstract: A reinforced ferrous metal casting and a method of making a reinforced ferrous metal casting wherein the reinforcing rods are located within tubular metal sheaths such that the metal sheaths become fused and bonded to the casting while the reinforcing rods located within the metal sheaths are not fused with respect to the sheaths and are, therefore, slidable within the casting. The reinforcing rods are preferably spaced from the sheath by a refractory coating.