Mercury - Water Separating Fuel Filter Fuel System Component Corrosion-Resistant Steel 18458T3. Overview. Clean fuel keeps your outboard running strong, and the Mercury Marine 18458T3 Water Separating Fuel Filter is built to do exactly that. Designed for 1995 and earlier Mercury and Mariner V6 TwoStroke EFI/DFI outboards, this filter protects your engine from both debris and water contamination. It features a 10-micron filtration element and a black screw-in water sensor, giving you the same rel