An outboard motor includes a cooling device which includes a supply passage supplying a cooling water taken into a lower unit to a cooling mechanism. A first shaft portion of the connecting mechanism has a cylindrical shape, is provided in an upper part of the lower unit, and has an axis coaxial with the axis of a drive shaft. A second shaft portion has a cylindrical shape, is provided in a lower part of an upper unit, and has an axis coaxial with the axis of the drive shaft. One shaft portion of the first and the second shaft portions is inserted into the other shaft portion to be pivotable relative to the other shaft portion. The drive shaft is inserted into the one shaft portion with a space. A part of the supply passage is formed of the space between the drive shaft and the one shaft portion.

A marine propulsion device for propelling a boat is provided The marine propulsion device includes a motor including an output shaft, a drive shaft configured to rotate upon receiving a rotation of the output shaft, a propeller shaft provided with a propeller and configured to be rotated upon receiving a rotation of the drive shaft, and a cooling device. The cooling device includes a cooling mechanism configured to cool the motor, and a water pump configured to send water outside the marine propulsion device to the cooling mechanism. An impeller of the water pump is connected via a one-way clutch to the output shaft, the drive shaft, or a rotation transmission member other than the drive shaft provided in the marine propulsion device and configured to rotate by the rotation of the output shaft.