Patent ID: 7156707

Claim:
A marine propulsion system to be driven by a motor, the system comprising: a propeller having a propeller hub and a plurality of propeller blades mounted on the hub; a drive for rotating the hub about a first axis; a propeller blade coupling mechanism for coupling the propeller blades to the hub so the propeller blades can be adjusted in pitch about respective axes transverse to the first axis; a push member for moving the coupling mechanism to thereby move the propeller blades and therefore adjust the pitch of the propeller blades, the push member having a screw thread; a nut member having a screw thread and engaging the screw thread of the push member; a control mechanism for rotating the nut to move the push member because of the engagement of the screw thread on the push member and the screw thread on the nut so the push member is moved to move the coupling mechanism to thereby adjust the pitch of the propeller blades; and the push member comprises a push rod and a bolt provided about the push rod so the push rod can rotate relative to the bolt, the screw thread of the push member being provided on the bolt, the bolt having a chamber for receiving a thrust portion of the push rod so that upon rotation of the nut in one direction, the bolt is moved in a first direction parallel to the first axis and the push rod is moved with the bolt whilst being able to rotate within the bolt because of the engagement of the thrust portion in the chamber, and upon rotation of the nut member in the opposite direction, the bolt and the push rod are moved in a second direction opposite the first direction parallel to the first axis because of the engagement of the thrust portion of the push rod in the chamber.