A self-contained hydraulic thruster for vessel. The hydraulic thruster incorporates a lower unit housing tiltably attached to a lower unit mounting tube attached to a base, a tube whose upper end is attached through the lower unit housing, and a shaft slidably disposed within the tube. A substantial length of tube extends downwards from the lower unit housing, thus providing support for the shaft. An actuator is disclosed which extends and retracts the shaft relative to the tube. A steering clamp is releasably attached to an end of the shaft which protrudes through the top of the lower unit housing. A steering clamp key traveling in a shaft keyway, or a shaft key in combination with a steering clamp keyway, help maintain constant the angular orientation between the steering clamp and the shaft. A steering gear meshing with a steering assembly, or an actuator driving a tie rod, provide steering.