Patent ID: 7909670

Claim:
A marine propulsion system comprising: an engine; a plurality of propellers that are 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 plurality of propellers with a speed thereof shifted to one of the lower speed reduction ratio and the higher speed reduction ratio during forward travel and reverse travel; an operation portion that is operated by a user to shift the transmission mechanism to the lower speed reduction ratio at least during the reverse travel; and a control portion that controls a shift of the transmission mechanism between the lower speed reduction ratio and the higher speed reduction ratio; wherein the control portion does not execute a shift from the higher speed reduction ratio to the lower speed reduction ratio when an engine speed of the engine is larger than a first threshold value even though the user operates the operation portion to shift the transmission mechanism from the higher speed reduction ratio to the lower speed reduction ratio.