An air passage and a cooling water passage can be formed in an intercooler provided on a small planing boat. A cooling water inlet of a cooling water passage in the intercooler can be provided at the lower end of the intercooler. A cooling water outlet can be at the upper end of the intercooler. The intercooler can be vertically elongated and disposed at the front side of the engine. Further, a discharge port of a supercharger can be directed upwardly and an air inlet of the intercooler can be provided on the intercooler at the upper part. Furthermore, the intercooler, the supercharger and an intake manifold can be arranged such that when viewed in the lateral direction, the intercooler and supercharger overlap each other and when viewed in the longitudinal direction, the intercooler and intake manifold can also overlap each other. Moreover, the intercooler can be of a two-pass type.