Control device for plural propulsion units

A propulsion unit control system for a vessel having plural propulsion units arranged side by side and electrically connected in association with two adjacent control levers that are controllable by an operator to operate a shift actuator and/or a throttle actuator of a corresponding one of the propulsion units, the control system comprising engine rotational speed detection devices adapted to detect an engine rotational speed of a reference propulsion unit and an engine rotational speed of a target propulsion, and a control device configured to control the engine rotational speed of the target propulsion unit, wherein the control device is adapted to synchronize the engine rotational speeds of the reference and target propulsion units by correcting the throttle opening of the target propulsion unit based on a deviation between the engine rotational speed of the reference propulsion unit and a natural engine rotational speed of the target propulsion unit that corresponds to a position of the control lever associated with the target propulsion unit, and the control device is configured so that, when synchronization of the engine rotational speeds is cancelled, the correction of the throttle opening of the target propulsion device is reduced stepwise from the corrected throttle opening to the natural throttle opening.