An outboard motor in which exhaust of an engine is emitted into water via an exhaust passage. The outboard motor comprises a throttle valve connected to an air intake port of the engine via an air intake manifold, a control motor for driving the throttle valve to open and close, and a controller for controlling the control motor. The controller controls the control motor such that the throttle valve fully closes when a determination is made that reverse rotation is occurring in the engine. The exhaust passage is communicated with the air intake manifold via a communication passage. A communication valve which opens only when reverse rotation is occurring in the engine is located at a portion where the communication passage and the air intake manifold connect.