Sierra fuel/water separator filter for Mercury Marine/Yamaha engine. Sierra fuel water separators remove over 98.8% of emulsified water from your gasoline. Sierra's 10 micron filters are over 90% efficient at removing particles as small as 10 micron. All filters flow @ 90 GPH to feed even the hungriest motor. Sierra 10 micron filters are recommended. 1/4" aluminum filter. Sierra Part #18-7982-2.