A hook assembly is arranged to engage with an engaged member to fix a first housing to a second housing of an outboard motor. The hook assembly includes a rotation shaft, a hook member, a lever, and a weight. The rotation shaft is rotatably mounted on the first housing. A recessed portion is provided in the hook member. The recessed portion is arranged to open in first rotation direction. The recessed portion engages with the engaged member. The lever extends from the rotation shaft in a second rotation direction opposite to the first rotation direction of the recessed portion. The weight regulates the rotation of the hook member in the second rotation direction when the hook member and the engaged member are engaged together. The arrangement provides a highly-operable hook assembly for the outboard motor that prevents disengagement even when an obstacle collides with the outboard motor during traveling of a boat.