PURPOSE: To enable reliable discharge of water in a water separation chamber and to prevent fuel from being left flowing from the water separation chamber even if an on-off valve is left opened, by providing a fuel forced feed pump, a check valve, formed between a water separating device and a fuel feed nozzle, and a pressure valve, prevented from opening depending upon a water head of fuel.

CONSTITUTION: When, after the interior of a fuel feed passage 23 is filled with fuel through operation of a manual fuel pump, an engine is started, a fuel pump 44 is driven to enable the feed of fuel in a tank to a carbureter 16. A moisture content in fuel is separated by a water separating device 38. By driving the manual fuel pump under a state to open an on-off valve 41 during the stop of an engine, water in the water separating device 38 can be drained. When an outboard engine is removed from a ship, even if, under a state in that a passage 23A on the engine side is separated from a passage 23B on the tank side, an on-off valve 41 is opened, a valve body 29 in a joint 24A keeps an airtight state, and check valves 51 and 52 also keep an airtight state. Therefore, an atmospheric pressure, exerted on the free end of a drain line 40, causes prevention of fuel in the water separating device 38 from outgoing.