To position an exhaust control valve and the pulley of a servo motor before installing the servo motor and the exhaust control valve, without using a jig and the like which are originally unnecessary.

A water jacket is provided in the exhaust manifold 80 of a two-cycle engine which is to be carried on a ship, and an exhaust control valve and a servo motor 110 are mounted on the exhaust manifold 80. The water jacket is supplied directly with cooling water from a jet pump. An adjuster 122 is mounted on the exhaust manifold 80 through a bracket 123.