Sierra Fuel Filter 18-7845 Long 21-Micron Marine Cartridge — 90 GPH Flow, OEM Fit for Mercury/Yamaha

The Sierra International 18-7845 medium fuel filter is a long, 21-micron replacement filter designed to protect outboard engines by removing fine particulates and water from ethanol-blended gasoline.

This fuel filter cartridge fits a range of marine applications and is built to the same fit-and-function specs as the OEM units it replaces. It maintains a 90 gallons-per-hour flow rate to supply even high-demand motors while trapping contaminants that can shorten engine life. The 18-7845 is compatible with specified Mercury and Yamaha part numbers, making it an easy swap for routine maintenance or emergency repairs.

Will this filter fit my Mercury or Yamaha outboard?

If your engine lists Mercury part 35-802893Q or Yamaha part ABB-FUELF-IL-TR, the Sierra 18-7845 is a direct replacement engineered to match the original dimensions and thread pitch. Check your current filter length and thread size to confirm compatibility.

• OEM equivalents: Mercury 35-802893Q, Yamaha ABB-FUELF-IL-TR
• Filter length: long — 435" (1105 mm) for compatible housings
• Thread pitch: 42690 to match factory fittings
• Simple swap-in installation for same-model housings

How does the 21-micron rating protect my engine?

A 21-micron rating captures smaller particles that can accelerate wear in fuel systems while still allowing high fuel flow. It balances filtration efficiency with the need for sufficient volume to feed aggressive fuel demands without starving the engine.

• Traps fine particulates down to 21 microns
• Maintains 90 GPH flow to support high-consumption engines
• Reduces sediment and debris reaching injectors and pumps
• Helps manage contaminants from ethanol-blended fuels

What features help with ethanol-blended fuels and water?

Sierra designed this filter with the realities of modern gasoline in mind: ethanol attracts water and loosens deposits. The media and construction reduce the risk of water and particulate contamination reaching critical engine components, improving reliability between services.

• Media optimized for ethanol-blend contamination control
• Construction assists in separating water and particulates
• Helps prevent injector and fuel-pump damage from debris
• Recommended for regular replacement as part of maintenance

How do I know when to replace this filter?

Replace the filter according to your engine manufacturer’s maintenance schedule or when you notice performance issues like rough idling, hard starting, or fuel starvation. Visual checks for water or heavy sediment in the filter bowl and scheduled interval replacements are standard best practices.

• Follow engine maker replacement intervals for best results
• Replace sooner if fuel system problems or contaminated fuel are suspected
• Inspect filter bowl for visible water or debris regularly
• Keep a spare on board for quick swap-outs during trips

Who is this for: The Sierra International 18-7845 suits boat owners and marine technicians who need a reliable, long-length medium filter that matches Mercury and Yamaha OEM specs. It’s ideal for users running ethanol-blended fuels, high-horsepower outboards, or anyone who wants a high-flow, 21-micron filtration option for routine maintenance and emergency replacements.

Key specifications summary: 21-micron rating, 90 GPH flow, long filter size 435" (1105 mm), thread pitch 42690, OEM cross-references Mercury 35-802893Q and Yamaha ABB-FUELF-IL-TR.