Mercury - Water Separating Fuel Filter Kit Mercury Racing 450R/500R & V12 Outboards Complete OEM Fuel Protection System 8M0166540. Overview. When you're running the kind of horsepower that Mercury Racing engines deliver, clean fuel isn't optional - it's essential. These engines breathe hard, respond instantly and rely on flawless fuel delivery to stay sharp. And when you're pushing offshore or running a long stretch at speed, you want the confidence that your powerplant is protected from water,