Air propulsion system for a boat comprises an internal combustion engine for powering a propeller in a single rotational direction. A pivoting mechanism pivots the propulsion system through a 360 degree arc about a transverse horizontal axis from a first position in which the propeller produce a forward thrust, through a second position in which the propeller produces a downward neutral thrust and a turning torque, to a third position in which the propeller produce a reverse thrust, to a fourth position in which the propeller produces an upward neutral thrust and a turning torque. The turning torque produced by the propeller turns the boat to the left in the second position and to the right in the fourth position. The engine is adapted to pivot with the propeller and continues to operate under throttle control in all pivoted orientations.