Abstract: There is provided a breather chamber structure. An inner wall partitions a breather space surrounded by outer walls into a plurality of chambers including a first chamber, a second chamber, and a third chamber. An inlet allows the gas to flow into the first chamber. A first communication path communicates between the first chamber and the second chamber. A second communication path communicates between the second chamber and the third chamber. An outlet allows the gas in the third chamber to flow out of the breather space. An oil discharge port is configured to return oil separated from gas in the breather space to an oil reservoir. The third chamber has a volume equal to or greater than half of a volume of the breather space. The first chamber has a volume larger than a volume of any of the chambers except for the first and third chambers.

Abstract: There is provided a breather chamber structure. An inner wall partitions a breather space surrounded by outer walls into a plurality of chambers including a first chamber, a second chamber, and a third chamber. An inlet allows the gas to flow into the first chamber. A first communication path communicates between the first chamber and the second chamber. A second communication path communicates between the second chamber and the third chamber. An outlet allows the gas in the third chamber to flow out of the breather space. An oil discharge port is configured to return oil separated from gas in the breather space to an oil reservoir. The third chamber has a volume equal to or greater than half of a volume of the breather space. The first chamber has a volume larger than a volume of any of the chambers except for the first and third chambers.

Abstract: An outboard motor includes a water jacket provided in a water-cooled engine, a first channel configured to allow a downstream-side end of a coolant flow of the water jacket to communicate with the external air, a thermo-valve provided between a downstream-side end of the coolant flow of the water jacket and an upstream-side end of the coolant flow of the first channel, a second channel configured to allow an upstream side of the coolant flow of the thermo-valve to communicate with the external air, and a second valve configured to open or close a second channel.

Abstract: An outboard motor includes a water jacket provided in a water-cooled engine, a first channel configured to allow a downstream-side end of a coolant flow of the water jacket to communicate with the external air, a thermo-valve provided between a downstream-side end of the coolant flow of the water jacket and an upstream-side end of the coolant flow of the first channel, a second channel configured to allow an upstream side of the coolant flow of the thermo-valve to communicate with the external air, and a second valve configured to open or close a second channel.