Patent ID: 7497750

Claim:
A water cooling system for an outboard motor, the system comprising a casing configured to be submerged in water at a lower part of the outboard motor and configured to support an internal combustion engine on an upper part thereof, an exhaust passage formed in the casing and configured to guide exhaust gas from the engine and through the upper part of the easing toward the lower part, a portion of the exhaust passage between an upstream-side passage and a downstream-side passage being configured to define an expansion chamber, a cooling water passage extending along the exhaust passage, and a drain port configured to permit water to be discharged into the exhaust passage at a point downstream of the expansion chamber after passing though the cooling water passage, wherein a first section of the cooling water passage extends along the upstream-side passage, wherein a second section of the cooling water passage extends along the expansion chamber, a second overflow opening is formed in the casing for connecting the upper part of the second section of the cooling water passage to the outside, and the second overflow opening is disposed below the first section of the cooling water passage.