Mercury - Water in Fuel Sensor - 8M0157779Water and fuel dont mix at least, not if you want your outboard running the way it should. Thats where the Mercury Marine Water in Fuel Sensor 8M0157779 comes into play. Mounted directly in your fuel system, this sensor constantly monitors for water contamination, giving you an early heads up before moisture works its way into injectors, pumps, or other critical components. Engineered specifically for select Mercury outboards, this OEM sensor