Sierra 18-7846 21 Micron Fuel Water Separator Filter Sierra high quality replacement Water Separating Fuel Filters are designed to be direct replacements of OEM filters. This fuel filter is specifically designed for the marine environment and todays ethanol blended fuels. Sierra canister fuel filters are epoxy coated to prevent corrosion inside the canister from reaching your fuel system. It is recommended to replace fuel filters every 50 hours of operation or at a minimum of once per year, pref