Sierra 18-7901 4-Cycle Outboard Oil Filter – Mercury/Mariner & Yamaha 8–9.9 HP
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Sierra 18-7901 4-Cycle Outboard Oil Filter – Mercury/Mariner & Yamaha 8–9.9 HP
Part Number: 18-7901 | SKU: 47-7901 | UPC: 808282100827
The Sierra 18-7901 is a spin-on oil filter for selected Mercury/Mariner and Yamaha 4-stroke outboard engines, primarily in the 8 HP and 9.9 HP range. It uses an M16 x 1.5 thread, heavy-wall steel canister with epoxy corrosion protection, and high-efficiency filter media that meets or exceeds OEM filtration requirements.
Key Specifications
- Thread: M16 x 1.5
- Filter type: 4-cycle outboard spin-on oil filter
- Canister: Heavy-wall epoxy-coated steel
- Filter media: High-efficiency, meets or exceeds OEM specification
- Marine-duty construction for freshwater and saltwater environments
Compatible Applications
- Mercury/Mariner 9.9 HP 4-stroke outboards, serial range 0H000058–0H017099 (1995–1998 applications)
- Mercury/Mariner 8 HP 4-stroke outboards — selected models (verify by serial number)
- Mercury/Mariner 9.9 HP 4-stroke outboards — other selected applications (verify by serial number)
- Yamaha F9.9 4-stroke outboards, approximately 1990–2003 (6G8-series filter reference)
- Yamaha T9.9 4-stroke outboards, approximately 1990–2003 (6G8-series filter reference)
Fitment Note: Confirm your engine model, model year, and serial number before ordering. The M16 x 1.5 thread and OEM cross-reference — Mercury 825467A1 or Yamaha 6G8-13440-00-00 — are the most reliable fitment identifiers for this filter.
Service Interval
Replace at every scheduled engine oil service. Follow the outboard manufacturer’s recommended interval for your specific engine model — typically every 100 hours or once per season, whichever comes first.
Installation Notes
- Remove the old filter and confirm the old gasket has come away with it — a retained gasket will cause an oil leak
- Clean the filter mounting surface
- Lightly coat the new filter gasket with fresh engine oil before threading it on
- Tighten by hand plus ¾ turn, or per engine manufacturer specification — do not over-tighten
- Run the engine and inspect for leaks before returning to service
OEM & Cross-Reference Part Numbers
- Sierra: 18-7901
- Mercury: 825467A1, 825467T1, 825467T02
- Yamaha: 6G8-13440-00-00
Related Products
- Sierra 18-7913 4-Cycle Outboard Oil Filter – Mercury & Honda — Sierra filter for larger Mercury 4-stroke outboards
- Sierra 7902 4-Cycle Outboard Oil Filter — Sierra filter for Yamaha 3FV/3FC-series 4-stroke outboards
- Seachoice 50-21004 Full-Flow Oil Filter – 20 Micron — Seachoice filter for Mercury 25–115 HP 4-stroke outboards
- Seachoice 50-21018 Full-Flow Oil Filter – 20 Micron — Seachoice filter for Yamaha 3FV/3FC-series 4-stroke outboards
Parts Desk Insights
Best Use Case: Routine oil and filter changes on older Mercury/Mariner 8 and 9.9 HP 4-stroke outboards from the mid-1990s through late-1990s, and on Yamaha F9.9 and T9.9 4-stroke outboards from 1990 through approximately 2003. This is a narrow-application filter covering older small-displacement 4-stroke outboards — useful for customers maintaining legacy engines that are still in service.
Common Issues: Because this filter covers a specific serial number range on Mercury/Mariner 9.9 HP engines, customers should confirm their serial number falls within the 0H000058–0H017099 range before ordering for Mercury applications. The M16 x 1.5 thread is a key differentiator from other small-outboard oil filters that look similar but use different thread specs. The fastest fitment check is matching Mercury 825467A1 or Yamaha 6G8-13440-00-00 to what is currently on the engine.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
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