Abstract: An average speed spinner water drive system for a center pivot irrigation system has a first group of sprinklers spaced along the main conduit which are continuously on, and a second group of pairs of sprinklers, each pair having an associated spinner drive which is sequenced on to drive the system. By sequencing sprinklers in combination with spinner drives, applicant's average speed system delivers an amount of water which is directly proportional to the speed of the system through the field. Each support tower is provided with a totally mechanical and hydraulic alignment control for sensing when it is behind the next outermost section of conduit and sequencing on its spinner drive to bring it into alignment. A percentage timer is used to set the speed of the system and thus the amount of water applied to the field. The percentage timer has a hydraulic motor turning a shaft with two individually adjustable cams to operate hydraulic start and stop valves.