Mercury Quicksilver OEM Under-Cowl Fuel Filter Kit 35-87946Q04 | 149 Micron | 6–60 HP 2-Stroke Outboard

Mercury Quicksilver OEM Under-Cowl Fuel Filter Kit — Part 35-87946Q04

• Part Number: 87946Q04
• Full Catalog Number: 35-87946Q04
• Brand: Mercury Marine / Quicksilver (Genuine OEM)
• Official Product Type: Fuel System Parts — Under-Cowl Fuel Filter Kit
• Filtration Rating: 149 micron
• Filter Type: Under-cowl bowl-style cartridge (not an inline barb filter or remote fuel-water separator)
• System: Outboard fuel delivery — engine-mounted under-cowl fuel filter bowl assembly
• Kit Contents: Replacement filter element / screen and Viton seal
• Application: Select Mercury and Mariner 6–60 HP 2-stroke outboards equipped with the screw-on bowl-style under-cowl fuel filter
• GTIN / UPC: 745061035522
• Weight: 30 g

Bowl-style under-cowl filter — not an inline or remote filter: 35-87946Q04 is the cartridge that installs inside the engine-mounted screw-on fuel filter bowl under the cowl. It is not an inline barb-style fuel filter or a remote fuel-water separator. The key fitment point is the screw-on bowl-style fuel filter housing on the engine. Mercury uses several different fuel filter types across outboards of similar horsepower — confirm the fuel-system diagram and filter housing style before ordering. This kit replaces the earlier all-white plastic filter element design with a current Quicksilver replacement.

What It Is

The 35-87946Q04 / 87946Q04 is the genuine OEM Mercury Quicksilver under-cowl fuel filter kit for applicable Mercury and Mariner 6–60 HP 2-stroke outboards. The filter element installs inside the engine-mounted fuel filter bowl and captures dirt, debris, and fuel-borne contamination before fuel reaches the carburetor, fuel pump, or fuel system components. The 149-micron rating makes this a pre-filter — it is designed to capture larger particulate contamination upstream of more sensitive fuel system components. The kit includes the replacement filter element and a Viton seal for the bowl. Mercury specifies this kit as the replacement for the earlier all-white plastic filter element design.

Compatible Applications

Confirm fitment by outboard serial number, fuel filter bowl style, and the Mercury parts diagram before ordering. Mercury and Mariner outboards of similar horsepower can use different under-cowl fuel filter configurations depending on production range and fuel system design.

• Mercury / Mariner 6 HP 2-stroke — where the Mercury parts diagram specifies 35-87946Q04
• Mercury / Mariner 8 HP 2-stroke — where specified
• Mercury / Mariner 9.9 HP 2-stroke — where specified
• Mercury / Mariner 10 HP Marathon, Sea Pro, and Viking — where specified
• Mercury / Mariner 15 HP, 15 Marathon, 15 Sea Pro, and Super 15 2-stroke — where specified
• Mercury / Mariner 20 HP and 20 Jet 2-stroke — where specified
• Mercury / Mariner 25 HP, 25 Marathon, and 25 Sea Pro 2-stroke — where specified
• Mercury / Mariner 30 HP 2-stroke — where specified
• Mercury / Mariner 40 HP and 40 Jet 2-stroke — where specified
• Mercury / Mariner 55 HP 3-cylinder 2-stroke — selected serial ranges including 0P325500 and up, 0T980000 and up
• Mercury / Mariner 60 HP 3-cylinder 2-stroke — selected serial ranges including 0P325500 and up, 0T980000 and up

Not sure it fits? Send us your Mercury or Mariner outboard serial number before ordering.

Kit Contents

• Replacement filter element / screen — 149 micron, bowl-style cartridge
• Viton seal for the filter bowl

Part Numbers & Cross-References

• 35-87946Q04 — Full Quicksilver OEM catalog number
• 87946Q04 — Mercury manufacturer number
• 87946K04 — Mercury-branded equivalent kit (selected applications — verify by diagram)
• 87946A3 / 87946Q3 / 87946Q0 — Earlier related Mercury filter references
• Sierra 18-7802 — Aftermarket cross-reference for the 87946 filter family (verify by serial number and parts diagram)

Related Fuel System Parts

On selected 55 HP and 60 HP 3-cylinder applications, 35-87946Q04 is used with filter assembly 891642T03. The related bowl seal is 897536. These are sold separately.

• Mercury Quicksilver Fuel Filter 879885K
• Mercury Quicksilver Fuel Filter 802893Q01
• Mercury MerCruiser Fuel Filter Kit 8M0088825
• Mercury MerCruiser Fuel Filter 8M0090809
• Mercury Quicksilver Fuel Pump Kit 892267A51
• Seachoice 10-Micron Fuel/Water Separating Filter Element — 2 & 4 Stroke Outboards

When to Replace

Replace the filter kit when:

• Annual fuel system service is due
• The 100-hour service interval has been reached
• Dirt, debris, or water contamination is visible in the filter bowl
• The engine shows hard starting, poor idle, hesitation, or fuel starvation symptoms
• Stale or ethanol-degraded fuel has been run through the system
• The filter element or bowl seal shows deterioration
• Tank contamination or water intrusion has been found in the fuel system

Service Interval

Replace annually or at every 100-hour service, whichever comes first. In boats used in ethanol-blend fuel environments, more frequent inspection is recommended — ethanol can cause debris from fuel tank linings and hoses to accumulate at the filter more rapidly. Replace sooner any time fuel starvation symptoms appear or contamination is found in the bowl during a visual inspection.

Installation Notes

• Shut off or isolate the fuel supply before opening the filter housing
• Remove the screw-on bowl carefully and discard the old filter element and seal
• Clean any contamination from the bowl interior before installing the new element
• Install the new filter element and the supplied Viton seal — do not reuse the old seal
• Reassemble the bowl correctly and hand-tighten first, then follow the Mercury service manual torque specification for the bowl retainer
• Prime the fuel system as required before starting
• Inspect carefully for fuel leaks at the bowl joint before returning the engine to service
• On 55/60 HP 3-cylinder applications, confirm that filter assembly 891642T03 and bowl seal 897536 are in serviceable condition while the filter is being replaced

Technical FAQ

Q: How do I know if my outboard uses this bowl-style filter?
Look under the cowling for a small bowl-style fuel filter assembly mounted on the engine — it will have a screw-on or twist-off transparent or semi-transparent bowl. If your outboard uses an inline barb-style filter connecting two fuel hose ends, or a remote fuel-water separator canister, a different service part is required. Confirm by serial number and the Mercury fuel-system diagram for the outboard.

Q: What does the 149-micron rating mean for my fuel system?
149 microns is a relatively coarse filtration rating, designed to capture larger particulate debris (dirt, rust, tank sediment) before fuel reaches the more sensitive downstream components such as the carburetor needle and seat or fuel pump. It is not a water-separating filter. For water separation, a separate fuel-water separator upstream of the engine is the appropriate solution.

Q: Is 87946Q04 the same as 87946K04?
87946K04 is a Mercury-branded equivalent kit used in selected applications. Confirm which number your fuel-system diagram specifies for the exact outboard model and serial number — they are functionally equivalent in most applications but should be verified against the OEM diagram before substituting.

Q: Can I use the Sierra 18-7802 aftermarket filter instead?
Sierra 18-7802 is a commonly listed aftermarket cross-reference for the 87946 filter family. Verify the cross-reference against your specific outboard’s serial number and fuel-system diagram before substituting an aftermarket filter for the OEM kit.

Q: Do I need to replace the bowl seal every time I service the filter?
Yes. The kit includes a Viton seal specifically because the bowl seal should be replaced at each service interval. Reusing an old, compressed, or fuel-swollen seal risks a fuel leak at the bowl joint after reassembly.

Parts Desk Insights

The most important distinction to communicate about 35-87946Q04 is the housing style — this is the cartridge for the engine-mounted screw-on bowl under the cowl, not an inline barb filter or a remote fuel-water separator. Customers who order this without confirming their filter housing style sometimes find they have the wrong part entirely. The second most common issue is customers replacing the filter element without replacing the bowl seal, then returning with a fuel leak at the bowl joint. The kit includes the seal specifically to prevent this — always replace both at the same service. Annual replacement is the right recommendation for any outboard used regularly, and pairing the filter service with spark plugs and gear oil makes for a clean annual maintenance order.