Jet propulsion unit for boats

Claim 1

In combination with a boat, a jet propulsion unit comprising: a. a boat hull including forward and rearward ends and having an intake opening intermediate said ends and a discharge opening at the rearward end disposed below the water line, b. a drive motor, c. a centrifugal pump mounted between said intake and discharge openings and including: 1. an impeller having a drive shaft, said shaft defining a substantially vertical axis of rotation and being connected to the motor in drive relation, and a coaxial inlet opening, and 2. a housing receiving the impeller in rotatable relation, d. a first intake passage extending longitudinaLly between the intake opening and the inlet opening of the pump impeller, e. a second discharge passage extending longitudinally between the pump housing and the discharge opening, f. a venturi unit mounted in the discharge passage, and g. cooling means for the motor including: 1. a water jacket disposed about said motor, 2. a first conduit extending between the first passage and the water jacket, and 3. a second conduit extending between the water jacket and the venturi throat to draw cooling water from the jacket by suction and thereby pick up water from the first passage through the first conduit for circulation through said jacket.