Mercury Quicksilver Inline Fuel Filter 879885Q

Part Number: 879885Q | Also listed as: 35-879885Q
Brand: Mercury / Quicksilver
Official Product Type: Under-Cowl Inline Fuel Filter 20-Micron, Translucent Body
Filtration Rating: 20 micron
System: Outboard Fuel Delivery (EFI / High-Pressure Fuel System)
Related part: 879885K (different suffix verify which applies to your engine by serial number)

A genuine OEM Mercury Quicksilver under-cowl inline fuel filter with a translucent plastic body that allows quick visual inspection of fuel condition and contamination without removing the filter. At 20 microns, this filter provides finer filtration than the 149-micron bowl-style element, capturing smaller particles before fuel reaches the high-pressure EFI system. Replacing it on schedule protects injectors, the fuel pump, and other sensitive fuel-delivery components.

Compatible Applications

Mercury FourStroke EFI 3040 HP where specified by serial number and parts diagram
Mercury FourStroke EFI 4060 HP 4-cylinder, where specified by serial number
Mercury FourStroke 75115 HP where specified by serial number
Mercury FourStroke EFI 150 HP where specified by serial number
Mercury Verado L4 and L6 135300 HP where specified by serial number

Fuel filter fitment varies by engine model, fuel system configuration, and serial number range. Always confirm part number 879885Q against your engine serial number and the Mercury parts diagram before ordering. Note that 879885Q and 879885K are different part numbers confirm which suffix your engine requires.

Part Details

Filter type: Under-cowl inline fuel filter translucent body with visual inspection window
Filtration rating: 20 micron (finer than the 149-micron bowl-style element)
Body material: Translucent plastic allows visual check of fuel colour and contamination
Installation: Replaces using existing hose clamps on applicable engines no additional hardware required
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. The translucent body allows you to check fuel condition between services replace sooner if contamination, discolouration, or restricted flow is visible, or if the engine shows hard starting, rough idle, hesitation, or fuel starvation symptoms.

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.
Reuse existing hose clamps if they are in good condition, or replace them if corroded or weakened.
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: What is the difference between 879885Q and 879885K?
A: Both are genuine Mercury inline fuel filters for similar applications, but the Q and K suffixes indicate different versions or production revisions. Always confirm which suffix is specified for your engine by checking the Mercury parts diagram for your serial number do not assume they are interchangeable.

Q: Why does the translucent body matter?
A: The clear body lets you visually check fuel colour and spot contamination water, debris, or discolouration during a quick inspection without removing the filter. On outboards that sit between trips, this is a useful early-warning indicator.

Q: How is this different from the bowl-style under-cowl filter (35-87946Q04)?
A: The 879885Q is an inline filter that connects directly into the fuel line. 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.

Parts Desk Insights

Best use case: This is the right filter for Mercury FourStroke EFI and Verado outboards where 879885Q is specified in the fuel-system diagram. The translucent body makes it a particularly good choice for outboards that sit for extended periods between uses a quick visual check during pre-season prep can catch fuel contamination before it causes a running problem on the water.

Common issues: The most frequent issue is confusion between the Q and K suffixes (879885Q vs. 879885K) both look similar and fit similar engines, but they are different part numbers. Always confirm the correct suffix by serial number before ordering. A second common issue is failing to depressurize the EFI fuel system before filter removal, which can result in fuel spray. Always follow the Mercury service manual procedure before disconnecting any EFI fuel line.