WATER JET PROPULSION UNIT FOR USE IN A JET BOAT

摘要

A water jet propulsion unit intended for use in jet boats, the unit comprisi ng an intake section (10), a pump section (12) and a nozzle section (16). In the pump section (12) there are two counter- rotating impellers (14, 15) on concentric counter-rotating shafts (26, 27) calibrated so that any radial flow created in the upstream impeller (14) is converted into axial flow by the down- stream impeller (15). In one embodiment the nozzle section (16) has a throttled outlet (17) 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 ( 10) in the preferred embodiment.