| 摘要 |
PROBLEM TO BE SOLVED: To provide a small-sized planing boat capable of rationally arranging an engine and an exhaust system, easily designing a cylinder head, and capable of improving output. SOLUTION: This small planing boat is provided with the four-cycle engine vertically having a crank chamber on the lower side and the cylinder head on the upper side, and the exhaust system; and is propelled by injection of water from a water jet pump driven by the engine. An exhaust passage Ea is formed in the cylinder head Eh in a manner of downwardly opening at a side part of a cylinder block Eb. A connecting block 2 having an exhaust passage 2A inside thereof, wherein a base end part is connected to an opening of the exhaust passage Ea and a tip part is connected to a base end opening of an exhaust manifold 1 positioned on a side part of the engine E, is integrally installed on the side part of the cylinder block Eb. A connection cooling passage 2B for connecting a cooling passage 1B in the exhaust manifold 1 and a cooling passage Ej in the cylinder block Eb is formed in the connecting block 2.
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