Sierra International 18-7844, Fuel Filter

The Sierra International 18-7844 is a short, 21-micron marine fuel filter designed to replace Mercury part numbers 35-807172 and 35-802893Q while delivering 90 GPH flow for dependable engine fueling.

This compact fuel filter from Sierra is built for small to mid-size outboard systems that require a high-flow, sub-25-micron element. It’s engineered to trap particulate contamination commonly introduced by ethanol-blended gasoline, while maintaining consistent fuel delivery at up to 90 gallons per hour. The unit uses a short-body design (listed as 3875" or 984mm) and a matching thread specification for straightforward OEM-style replacement.

How does the 21-micron rating affect engine protection?

A 21-micron element captures medium-size particles that can wear injectors, carburetors, and fuel pumps without restricting normal fuel flow. It’s a balance between fine filtration and maintaining a high flow rate for hungry outboards.

• Traps sand, rust, and larger particulate down to 21 microns
• Reduces abrasive wear on fuel system components
• Helps maintain consistent performance in marine environments

Will this filter work with Mercury engines requiring part 35-807172?

Yes — the Sierra 18-7844 is specified as a direct replacement for Mercury Marine OEM 35-807172 and also fits 35-802893Q applications. It matches the form, fit, and functional needs for those models so you can swap it into existing mounts and lines.

• OEM cross-reference: MERCURY MARINE 35-807172
• Compatible with applications calling for 35-802893Q
• Designed for like-for-like installation without custom adaptors

How does this filter handle ethanol-blended fuels?

Ethanol in modern gasoline tends to attract and hold water and can loosen deposits that then circulate in the fuel system. The Sierra element helps remove loosened particulates, protecting downstream components and reducing clogging risk compared with no filtration.

• Captures particulates stirred up by ethanol and moisture
• Prevents larger debris from reaching injectors and pumps
• Supports reliable engine starts and consistent running

What are the key physical and performance specs to know?

This short filter is built to provide reliable flow and a correct mechanical interface with compatible Mercury systems. It balances a compact size with the capacity needed for many marine fueling demands.

• Flow rate: 90 GPH to supply high-demand motors
• Filter rating: 21 micron for medium-level particle capture
• Filter size: Short - listed as 3875" or 984mm (use OEM fitment as guide)
• Thread pitch: 42690 to match standard mounting

Who is this for? The Sierra International 18-7844 is aimed at boat owners, mariners, and service technicians who maintain Mercury-compatible outboards and need a compact, high-flow replacement filter that handles ethanol-blended fuels. It’s suited for routine service intervals, pre-season maintenance, or anytime a direct OEM-equivalent replacement is required to keep fuel systems clean and engines running reliably.