Waterjet with internal drive motor

1. A marine waterjet propulsion system comprising: an impeller with an impeller hub; a diffuser with a diffuser hub; at least one impeller bearing; a motor driving the impeller; and a closed-circuit lubrication and cooling system having a lubricant cooler, a circulation pump, and at least one hollow shaft forming at least one lubricant channel, the motor, the bearing(s) and the lubrication and cooling system being inside at least one of the impeller hub and the diffusor hub.

2. The marine waterjet propulsion system of claim 1 wherein the motor is an electric motor.

3. The marine waterjet propulsion system of claim 1 wherein the motor is a hydraulic motor and the hydraulic motor serves as the circulation pump.

4. The marine waterjet propulsion system of claim 1 further including a transmission, connecting the motor in a drive relationship with the impeller.

5. The marine waterjet propulsion system of claim 4 wherein the lubrication and cooling system also cools the transmission.

6. A marine waterjet propulsion system having:

an impeller with an impeller hub and at least one impeller bearing;

a diffuser with a diffuser hub;

a motor with a hollow motor shaft driving the impeller through a transmission, the motor being inside at least one of the impeller hub and the diffusor hub;

an oil circulation pump for pumping oil through the at least one bearing, the motor, and the transmission for lubrication;

an oil cooler through which oil is pumped for heat removal; and

at least one hollow shaft, the at least one hollow shaft and the motor shaft being oil channels to lubricate the at least one bearing.

7. The marine waterjet propulsion system of claim 6 wherein the motor is an electric motor.

8. The marine waterjet propulsion system of claim 6 wherein the motor is a hydraulic motor.