An apparatus for reducing vibration on a ship with at least two drive shafts by determining and utilizing an optimum angular offset which corresponds to a minimum vibration level. The apparatus comprises a servo-control circuit for servo-controlling the angular difference between the two shafts to a reference value. A calibration circuit determines the optimum angular offset between the shafts corresponding to the minimum vibration level. A control circuit responds to a control signal by actuating in succession the calibration circuit and then the servo-control circuit, wherein the optimum angular offset is set to the reference value.