To prevent the lowering of the engine speed in the clutch-in operation of a shift device in a clutch mechanism with a simple structure.

In an outboard motor comprising a carburetor 15 where a throttle valve is open and close operated by the throttle switching devices 19-23 and a clutch mechanism to be clutched in by a shift device 25, the throttle valve is open operated interlocking with the shift device 25 when the clutch mechanism is clutched in through the shift device 25, whereby the trawling rotational frequency of an engine 5 is increased.