| 摘要 |
PROBLEM TO BE SOLVED: To improve engine output. SOLUTION: This small-sized plaining boat is provided with an independent exhaust passages 40a to 40d, which extend independently from respective exhaust ports 26a to 26d of a multi-cylinder engine 6, a collective exhaust passage 44 for collecting the independent exhaust passages 40a to 40d into one, and a cooling means for cooling at least a part of the exhaust passages 40a to 40d and 44, by supplying cooling water to a water jacket 41 formed on the outer periphery of the exhaust passages 40a to 40d. Passage sectional areas D1 to D4 of approximately the whole length of respective independent exhaust passages 40a to 40d are formed, so that the independent exhaust passages 40a to 40d having the longer passage length is the larger sectional area, and the water jacket 41 is formed over substantially the whole length of respective independent exhaust passages 40a to 40d. |
