Mercury Quicksilver Inline Fuel Filter 879885K | EFI FourStroke & Verado Outboard
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Mercury Quicksilver Inline Fuel Filter 879885K
Part Number: 879885K | Also listed as: 35-879885K
Brand: Mercury / Quicksilver
Official Product Type: Under-Cowl Inline Fuel Filter — EFI Outboard
Fuel Line Connection: Approx. 8 mm / 5⁄8-inch inline
System: Outboard Fuel Delivery (EFI / High-Pressure Fuel System)
A genuine OEM Mercury Quicksilver under-cowl inline fuel filter for applicable Mercury FourStroke EFI and Verado outboards. Installed in the fuel line beneath the engine cowl, this filter captures particles and moisture before fuel reaches the high-pressure EFI system — protecting injectors, the fuel pump, and other sensitive fuel-delivery components. Replacing it on schedule is one of the most cost-effective ways to maintain reliable starting and smooth performance on EFI outboards.
Compatible Applications
- Mercury FourStroke EFI 30–40 HP — 3-cylinder, where specified by serial number
- Mercury FourStroke EFI 40–60 HP — 996 cc, where specified by serial number
- Mercury FourStroke EFI 75–115 HP — 1.7L and 2.1L, where specified by serial number
- Mercury FourStroke EFI 150 HP — where specified by serial number
- Mercury Verado L4 and L6 135–300 HP — where specified by serial number
Fuel filter fitment varies by engine model, fuel system configuration, and serial number range. Always confirm part number 879885K against your engine serial number and the Mercury parts diagram before ordering.
Part Details
- Filter type: Under-cowl inline fuel filter (not a bowl-style element or remote fuel-water separator)
- Connection size: Approx. 8 mm / 5⁄8-inch inline fuel line
- Application: EFI and high-pressure fuel systems on Mercury FourStroke and Verado outboards
- OEM status: Genuine Mercury / Quicksilver — not aftermarket
- Diagram position: In-line in the fuel supply line under the engine cowl — confirm exact location in the Mercury fuel-system diagram for your outboard
Service Interval
Replace annually or at every 100-hour service, whichever comes first. Also replace sooner if the engine shows hard starting, rough idle, hesitation, lean running, or fuel starvation symptoms — or after stale fuel, ethanol-related debris, or tank contamination events.
Installation Notes
- Relieve fuel system pressure before disconnecting the filter on EFI engines — refer to the Mercury service manual for the correct depressurization procedure.
- Note the flow direction arrow on the filter body and install in the correct orientation.
- Ensure both inline connections are fully seated and secure before starting the engine.
- After installation, prime the fuel system, inspect for leaks, and run the engine to confirm stable operation.
Technical FAQ
Q: How is this filter different from the bowl-style under-cowl filter (35-87946Q04)?
A: The 879885K is an inline filter — it connects directly into the fuel line with barb or push-connect fittings. The 35-87946Q04 is a bowl-style element that sits inside a reusable housing. They are not interchangeable. Confirm which style your engine uses by checking the fuel-system diagram for your serial number.
Q: Does this filter fit both carbureted and EFI outboards?
A: This filter is designed for EFI and high-pressure fuel systems. Carbureted outboards typically use a different filter style. Confirm by serial number and fuel-system diagram.
Parts Desk Insights
Best use case: This is the correct OEM inline filter for Mercury FourStroke EFI and Verado outboards where 879885K is specified in the fuel-system diagram. It is most commonly ordered as part of an annual EFI service alongside spark plugs and gear oil. On high-pressure EFI systems, a clogged or bypassed fuel filter can cause injector damage that is far more expensive than the filter itself.
Common issues: The most frequent issue is customers ordering this inline filter when their engine actually uses the bowl-style element (35-87946Q04), or vice versa — always confirm the filter style under the cowl before ordering. A second common issue on EFI engines is failing to depressurize the fuel system before filter removal, which can result in fuel spray. Always follow the Mercury service manual depressurization procedure before disconnecting any EFI fuel line.
Related Parts
- Mercury Quicksilver Under-Cowl Fuel Filter Kit 35-87946Q04 | 6–60HP Outboard
- Mercury MerCruiser Quicksilver Fuel Filter 802893Q01
- Mercury MerCruiser Fuel Filter Kit 8M0088825
- Mercury MerCruiser Fuel Filter 8M0090809
- Mercury MerCruiser Fuel Filter Kit 8M0106635
- Mercury MerCruiser Quicksilver Fuel Pump Kit 892267A51
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
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