An outboard motor comprising: an engine including a fuel injection device (21,22); a fuel tank including an internal space in which a fuel is storable; a fuel pathway connected to the fuel injection device (21,22) and the fuel tank; a fuel pump disposed in the fuel pathway, the fuel pump being configured to supply the fuel from the fuel tank to the fuel injection device (21,22); and a controller programmed to control the fuel pump and to determine whether or not a start condition indicating that an air has entered the fuel pathway is satisfied, characterised in that the controller programmed to determine whether or not a start condition 1 is satisfied, the start condition 1 is that an output of the fuel pump has been kept maximum for a predetermined period of time, wherein when the start condition 1 is satisfied, the controller is programmed to execute fuel running-out determining control, in the fuel running-out determining control, the controller is programmed to drive a sub pump, and simultaneously, programmed to determine whether or not a start condition 2 is satisfied, the start condition 2 is that the output of the fuel pump has been kept maximum, wherein when the start condition 2 is satisfied, the controller is programmed to execute a pump limiting control, in the pump limiting control, the controller is programmed to lower un upper limit of the output of the fuel pump, additionally, during the pump limiting control, the controller is programmed to determine whether or not a start condition 3 is satisfied, the start condition 3 is that engine stalling has occurred or that an engine switch is set in an off position, wherein when the start condition 3 is satisfied, the controller is programmed to execute an air releasing control to open the fuel injection device (21,22) and drive the fuel pump. an engine including a fuel injection device (21,22); a fuel tank including an internal space in which a fuel is storable; a fuel pathway connected to the fuel injection device (21,22) and the fuel tank; a fuel pump disposed in the fuel pathway, the fuel pump being configured to supply the fuel from the fuel tank to the fuel injection device (21,22); and a controller programmed to control the fuel pump and to determine whether or not a start condition indicating that an air has entered the fuel pathway is satisfied, characterised in that the controller programmed to determine whether or not a start condition 1 is satisfied, the start condition 1 is that an output of the fuel pump has been kept maximum for a predetermined period of time, wherein when the start condition 1 is satisfied, the controller is programmed to execute fuel running-out determining control, in the fuel running-out determining control, the controller is programmed to drive a sub pump, and simultaneously, programmed to determine whether or not a start condition 2 is satisfied, the start condition 2 is that the output of the fuel pump has been kept maximum, wherein when the start condition 2 is satisfied, the controller is programmed to execute a pump limiting control, in the pump limiting control, the controller is programmed to lower un upper limit of the output of the fuel pump, additionally, during the pump limiting control, the controller is programmed to determine whether or not a start condition 3 is satisfied, the start condition 3 is that engine stalling has occurred or that an engine switch is set in an off position, wherein when the start condition 3 is satisfied, the controller is programmed to execute an air releasing control to open the fuel injection device (21,22) and drive the fuel pump.