PURPOSE: To lower a footing of the ship controller and stably operate work in a ship and its control, by mounting an engine case and intermediate shaft casing behind the engine case of the small ship as an integral unit to a ship body.

CONSTITUTION: An engine 8 mounted to a ship body 1 and stern drive 16 mounted to a transom 13 are connected by an intermediate shaft 80. A casing of this engine 8 and inverted U-shaped sectional intermediate casing 3 are integrally formed by fiber reinforced plastic and mounted to a ship bottom and internal side of the ship body 1. Here the casing 3 is positioned only in the central part to place a footing of the controller 4 to a low position in both side parts of the casing, when ship control and work in a ship can be stably operated.