| 摘要 |
PROBLEM TO BE SOLVED: To enhance intake efficiency by contriving the layout of the intake system of a four-cycle engine and to incorporate in a compact fashion the engine into below an astriding seat. SOLUTION: In a jet-propelled boat in which a four-cycle engine 20 extending a crankshaft 28 in the back and fort directions of a boat body 10 is positioned below an astriding seat 15 for mounting in the boat body, an intake passage 20i communicating with each intake port of the cylinder head 20h of the engine 20 and an intake tube 39 connected to each intake passage 20i are placed to form generally a linear shape toward diagonally up to the upper part. Each intake tube 39 at its upper end part is connected to a connecting tube 40. An intake box 42 positioned at a side of the engine 20 is connected to an intake connecting tube 43 downwardly extended from the connecting tube 40.
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