A water jet propulsion system for watercraft having an impeller, especially a conical oblique flow impeller with an increased outer diameter in going toward the downstream side. The impeller is secured to a transmission shaft which is journalled by bearings in a hub of fixed blades and formed at its...http://www.google.com.au/patents/US4541808?utm_source=gb-gplus-sharePatent US4541808 - Water jet propulsion system
