To facilitate clutch operation by correcting a base control rate in relation to at least fuel injection at the time of clutch switching, reduce a fuel injection rate, and decelerating engine rotational speed, in an internal combustion engine in which regulation of a throttle opening degree and switching of a clutch are interlocked with each other, such as an outboard motor.

High surface pressure is applied between a dock clutch 19 and a advance gear 15 or a rearward travel gear 17 which are engaged with the clutch 19, at the time of engine high rotation. In the case where an operating lever is operated at this time and the clutch 19 is disconnected from the gear 15 or the gear 17, large tension is applied on a shift cable. Tension applied on the shift cable is detected by a shift switch, ignition of a specified cylinder is stopped by a control device when tension exceed a prescribed value, and then it is controlled so as to decelerate engine rotational speed. It is thus possible to disconnect the clutch 19 from the gear 15 or the gear 17, and it is possible to facilitate clutch operation.