A swivel bracket can be attached to a transom plate of a watercraft by means of a clamp bracket. A steering bracket can be rotationally provided in a swivel shaft of the swivel bracket. An outboard motor body can be secured to the steering bracket. An electric motor can be housed in the outboard motor and engaged with a stationary gear secured to the swivel bracket by way of a reduction gear. Driven by the electric motor, the steering bracket turns relative to the swivel bracket, causing the outboard motor body to turn.