Patent ID: 8162708

Claim:
A marine propulsion system comprising: an engine; a propeller that is rotated by the engine; a transmission mechanism that operates in at least a lower speed reduction ratio and a higher speed reduction ratio, and transmits a driving force of the engine to the propeller with a speed thereof shifted to one of the lower speed reduction ratio and the higher speed reduction ratio; a speed detection portion that detects a speed of a hull propelled by a rotation of the propeller; and a control portion that controls a shift between the lower speed reduction ratio and the higher speed reduction ratio of the transmission mechanism; wherein the control portion controls a shift between the lower speed reduction ratio and the higher speed reduction ratio of the transmission mechanism; and the control portion controls the transmission mechanism based on a first shift control map which provides a reference for a shift between the lower speed reduction ratio and the higher speed reduction ratio of the transmission mechanism based on the speed of the hull and the rotational speed of the propeller.