Mercury - On-Engine Water Separating Fuel Filter V6/V8 FourStroke Series Composite Filtration 8M0176313. Overview. Every boater has a moment when they realize just how much they depend on clean, steady fuel. Maybe it happens on a long run back through choppy water, or while idling into a quiet marina at sunset. When your engine breathes clean fuel, everything feels smoother - the throttle responds the way it should, the boat settles into its rhythm, and you can relax knowing your powerplant is b