Mercury - Quicksilver Water Separating Fuel Filter Kit Fuel System Component Corrosion-Resistant Steel 18458Q3. Overview. Fuel and water don't mix, and when they do, engines pay the price. The Mercury Marine 18458Q3 Quicksilver Water Separating Fuel Filter Kit keeps your fuel clean and your engine protected. Designed for Mercury and Mariner V6 EFI outboards (1995 and earlier), this kit includes both the 10-micron filter element and a black plastic water warning sensor that alerts you when water'