Sierra Fuel/Water Separator Filter 18-7866 — 10 Micron High-Capacity 6" Element, 90 GPH

Keeping fuel clean is critical for modern marine engines; the Sierra 18-7866 fuel water separator combines fine 10-micron filtration with a high-capacity 6-inch element to catch particles and separate emulsified water before it reaches sensitive fuel injection components. Built as a direct replacement for common OEM filters (including Yamaha MAR-FUELF-IL-TR), this element balances efficient contaminant removal with the flow rates needed by larger 2-stroke and 4-stroke outboards.

How does the 18-7866 protect my Yamaha outboard?

The filter traps particles down to 10 microns and separates emulsified water, reducing the risk of clogged injectors or fuel system damage. Its construction is optimized for marine conditions and slippery contaminants commonly found in stored or contaminated gasoline.

• 10-micron media removes fine particles and contaminants
• Removes over 99.8% of emulsified water from gasoline
• High-capacity 6-inch element extends service intervals
• Designed for marine fuel system durability and corrosion resistance

Will this filter maintain engine performance at high flow demand?

Yes — the Sierra 18-7866 delivers up to 90 gallons per hour, providing the flow required by high-horsepower outboards without compromising filtration. That throughput helps ensure steady fuel delivery under heavy throttle while keeping contaminants out of the engine.

• Rated flow: 90 GPH suitable for large outboards
• High-capacity element reduces pressure drop during peak demand
• Compatible with fuel injection systems needing consistent supply

Is the 18-7866 a direct replacement for my OEM filter?

The 18-7866 is manufactured to match the fit and function of several OEM filters and is intended as a direct replacement for common Yamaha and other manufacturers' part numbers. Thread sizing and element height match high-capacity OEM specifications for straightforward swap-outs.

• Replaces Yamaha MAR-FUELF-IL-TR and MAR-10MEL-00-00
• Cross-references Mercury 35-8M0154754 and Mallory 9-37807
• 11/16-16 thread and 6" element height for proper fit

How should I maintain and service this fuel water separator?

Regular inspection and replacement on a schedule aligned with your boat use will keep the separator effective; change the element if you detect water in the bowl, reduced engine performance, or as part of routine seasonal service. Follow manufacturer torque and installation guidance to ensure a leak-free seal.

• Inspect filter bowl and element seasonally or after fuel issues
• Replace element if water or heavy contamination is present
• Use correct thread seal and torque per service manual
• Dispose of used elements according to local regulations

Who is this for: The Sierra 18-7866 is aimed at owners and technicians of high-horsepower Yamaha outboards and other compatible engines who need reliable fuel filtration that balances fine particle removal with high flow. Choose this element if you run fuel-injected or sensitive fuel systems, operate in coastal or variable-fuel conditions where water and contaminants are a concern, and prefer a long-lasting, OEM-compatible replacement backed by Sierra's limited lifetime warranty.