Mercury - Inline Fuel Filter Element Under-Cowl Fuel System Fine Mesh Polymer 87946Q04. Overview. If you've ever had a great day on the water cut short by a sputtering engine, you know just how much clean fuel matters. Those quiet moments at sunrise, the slow push out of the harbor, the long run back across choppy water-all of it depends on your outboard breathing a steady, clean stream of gasoline. The Mercury 87946Q04 Inline Fuel Filter Element is one of those small, behind-the-scenes parts th