Abstract: The present invention provides an offset control mechanism and a variable blade-pitch mechanical kinematic system for cycloidal propellers. This is achieved by the concentric positioning of the drive shaft, the variable offset circular guide track, the eccentric X-Y slide plates, the propeller hub and the variable blade-pitch kinematic linkages, all about the axis of propeller rotation. The control actuation system is free-flooded in water and non-rotating, yet in close proximity to the rotating propeller hub. The pitch of each propeller blade is cyclically varied by the kinematic levers on each blade following a circular guide track during each revolution. Additionally, the circlar track swivel guide in the blade lever kinematics can also lever a trailing blade-flap to provide additional cyclic propeller lift in the direction of motion. The propeller improvements include a low-drag propeller hub and a variable-pitch blade ground plane ring about the ends of the blades.