Sierra 18-7844 Water Separating Fuel Filter for Sterndrives and Outboards Sierra replacement water separating fuel filter for use with Mercury and Mercruiser engines. Sierra fuel water separators remove over 99.8 of emulsified water from your gasoline. Sierras 21 micron canister filters feature an epoxy-coated steel canister that prevents corrosion inside the canister from reaching your fuel system. These durable filters are pressure and leak tested to ABYC and USCG standards. All filters flow a