Mercury - 816296K2 Inline Fuel Filter Mercury & Mariner Outboards 5/16-Inch Fuel Line 816296K2. Overview. Clean fuel makes all the difference in how your outboard runs. The Mercury 816296K2 Inline Fuel Filter helps keep your Mercury or Mariner outboard protected from moisture, rust, and other contaminants that can clog carburetors and steal performance. Designed to fit the 5/16-inch fuel line under the cowl, it's a simple, transparent filter that gives you both peace of mind and a quick visual c