To provide a safe outboard motor of a racing boat, which prevents electric shock when detaching/attaching a battery unit equipped with a battery from/to the outboard motor.

In a state in which a battery unit 4 is detached from a motor unit 3, terminals T1 and T3 are disconnected from each other, and terminals T2 and T4 are disconnected from each other, and a reed switch 10 is separated from a magnet 26, consequently the reed switch 10 is opened. As a result, a protective relay 7 is demagnetized to open a switch 7A, and the power supply from a battery cell 6 to the terminals T1, T2, and the terminals T3, T4 is stopped, so that any current does not run between the terminals T1, T2 of the battery unit 4.