Abstract: A side thruster comprises a valve, a first water passageway, a second water passageway, a third passageway, a fourth passageway and a pump having an inlet and an outlet. The valve housing includes a first, second, third and fourth ports and a two-position barrier situated within the housing. When in the first position, the barrier connects the first port with the second port and the third port with the fourth port. When in the second position, the barrier connects the second port with the third port and the fourth port with the first port. The first passageway extends between the first port and a first side opening on a first side of the boat. The second passageway extends between the third port and a second side opening on a second side of the boat. The third water passageway extends between the second port and the pump outlet. The fourth water passageway extends between the pump inlet and the fourth port.