Sierra 18-7944 Fuel Water Separator Filter Sierra replacement fuel water separator filter for use with Mercury and Mercruiser engines. Sierra fuel water separators remove over 99.8 of emulsified water from your gasoline. Sierras 10 micron filters are over 90 efficient at removing particles as small as 10 micron. All filters flow at 90 GPH to feed even the hungriest motor. Sierra 10 micron filters are recommended to prevent damage to sensitive inboard and outboard fuel injection systems. Features