| 摘要 |
To provide an internal combustion engine for a small-sized planing boat in which a part that enlarges the internal combustion engine by a balancer shaf t is inhibited in a possibly small range and the internal combustion engine is made compact. The invention is characterized in that balancer shafts for preventing secondary vibration are arranged together with a crankshaft on a dividing plane of a crankcase and a cylinder block of an internal combustion engine mutually in parallel, a crankshaft bearing by which the crankshaft is held so that the crankshaft can be rotated is formed in the crankcase and th e cylinder block on a dividing plane of plural mutually opposite ribs planted in a longitudinal direction, a balancer shaft bearing by which the balancer shafts are held so that the balancer shafts can be rotated is formed on a dividing plane of a selected longitudinal pair of ribs of the plural ribs in the longitudinal direction and the balancer shaft bearing is biased in a directi on in which the balancer shaft bearing approaches the other rib in at least one ri b of the longitudinal pair of ribs, compared with the crankshaft bearing.
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