Patent ID: 7270583

Claim:
A propulsion system for a watercraft, comprising: a tunnel formed in a hull of said watercraft, said tunnel defining a concavity having a longitudinal axis of symmetry coincident with a longitudinal axis of symmetry of said watercraft; said concavity having a trailing end substantially coincident with a transom of said watercraft and said concavity having a leading end disposed forwardly of said transom; said concavity having a minimum depth at said leading end and a maximum depth at said trailing end; an impeller mounted in said trailing end of said concavity; a stator mounted externally of said concavity in trailing relation to said impeller; an engine positioned forwardly of said concavity, said engine having an output shaft; an elongate drive shaft extending from said output shaft of said engine to said impeller; a top wall of said concavity being sloped at an angle between twenty to thirty degrees (20-30°); an intake grate disposed in a mouth of said concavity; said top wall of said concavity being substantially flat near said leading end of said concavity and gradually increasing in curvature toward said trailing end of said concavity, said top wall of said concavity having a substantially semicircular shape at said trailing end of said concavity; a circular housing that circumscribes said impeller, said circular housing being mounted in said trailing end of said concavity; said stator including a plurality of non-rotatable vanes and said stator including a circular housing that circumscribes said vanes; a nozzle disposed in trailing relation to said stator; and a rudder disposed in trailing relation to said nozzle; whereby said slope of said top wall ensures that said concavity is completely full of water even when the watercraft is traveling at high speeds; whereby water flowing through said intake grate encounters no obstacles other than said elongate drive shaft before encountering said impeller; whereby water flows through said concavity in a laminar flow; and whereby said impeller, stator, and rudder are protected from damage caused by underwater obstacles.