A single switch unit having a pair of switches is provided in the vicinity of a throttle grip which is provided in a distal end of a tiller handle. The single switch unit is provided with a function of performing the operation for changing a tilt angle of an outboard motor body with respect to a hull and a function of performing the operation for adjusting a rotational speed of an engine of the outboard motor at the time of trolling operation. Upon simultaneous pressing of a pair of the switches, these two functions of the switch unit are switched.