A pedal propulsion system for a transportation conveyance comprises a pedal drive assembly having a teethed synchronous drive belt engaged between a drive sprocket and a transfer sprocket. The rotational axes of the transfer sprocket and the drive sprocket are oriented at an angle of up to 90 degrees from one another. The rotation of the transfer sprocket is conveyed to a propeller drive assembly mounted at the rear of a water craft by an elongated rotary shaft and a flexible transmission drive cable to facilitate removable of the propulsion system from the transportation conveyance.