PURPOSE: To effectively utilize the space for storing a battery and a fuel tank independently by partitioning the fuel tank housing and the adjacent battery housing by the side wall of a container.

CONSTITUTION: A container 8 is formed so as to separate the floor 2 and the motor well 3. A fuel tank 83 is stored in the container 8. A seat 81 is formed on the upper surface of the starboard side of the container 8. The central part of the upper surface of the container 8 is convered with a hatch cover 82. The floor 2 is extending continuously between the port side of the container 8 and the hull wall 4 forming a housing 22 for storing the battery 84. Accordingly, the container 8 storing the fuel tank 83 and the housing 22 for battery 84 are partitioned by the side wall of the container 8 so that the battery can be stored safely and adjacently to the fuel tank.