A thruster unit for generating side thrust for improved maneuverability of a marine vessel employs a peripherally-driven propeller situated below the waterline and remotely powered by a motor situated above the waterline via a flexible drive member. The propeller is supported by a rolling element bearing disposed circumferentially around the outer perimeter of the propeller providing both axial and radial support. The lower portion disposed for submerged operation has a substantially thin cross section with a narrow thickness aligned transversely to the vessel to operate hydro-dynamically while the vessel is underway. This makes it possible for the present invention to remain in the operating position indefinitely even while the vessel is in motion without risking a structural damage. The thruster unit can be installed on the vessel using a hinged bracket assembly such that during the extended periods while the vessel is not operating the thruster unit may be pivoted out from the water for dry storing, safely away from the corrosion, marine growth, or any other harmful effect of the water.