Quicksilver 1/4-28 Jam Nut 8267139 | Mercury MerCruiser OEM Flame Arrestor Mounting
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Quicksilver OEM 1/4-28 Jam Nut — Part No. 8267139 / 11-8267139
- Part Number: 8267139
- Service Format: 11-8267139
- Supersedes: 28941 → 8267139 (current)
- Brand: Quicksilver (Genuine Mercury Marine OEM)
- Type: Jam Nut / Mounting Nut
- Thread: 1/4-28 UNF (fine thread)
- Nominal Thread Diameter: 0.250 in. / 6.35 mm
- Thread Pitch: 28 TPI / approx. 0.91 mm
- Quantity: 1
- GTIN / UPC: 745061464575
- System: Fuel / Carburetor — flame-arrestor mounting and related Mercury assemblies
What This Part Does
This genuine OEM jam nut locks the flame-arrestor mounting stud in position on compatible Mercury carbureted engines. Mercury parts diagrams identify 8267139 as the lower jam nut on the flame-arrestor mounting stud arrangement — it secures the stud against loosening under engine vibration. Some dual-carburetor arrangements use two of these nuts as the bottom stud-mounting nuts.
Critical thread note: This is a 1/4-28 UNF fine-thread nut. Do not substitute a visually similar 1/4-20 UNC coarse-thread nut — it will appear to fit initially but will not properly engage the stud threads, risking damage to the stud and loss of flame-arrestor retention. Match by OEM part number, not by visual appearance.
Compatible Applications
- Mercury flame-arrestor mounting stud assemblies on selected carbureted engines
- Carburetor / flame-arrestor assemblies where the diagram specifies 8267139 / 11-8267139
- Selected Mercury / MerCruiser gasoline engines with carburetor-mounted flame arrestors
- Selected Bravo and sterndrive assemblies where a 1/4-28 nut is specified
- Any Mercury or MerCruiser assembly where the current parts diagram calls for 8267139
Confirm the exact diagram position and required quantity using your engine model and serial number before ordering.
Superseded Part Numbers
- 28941 → 8267139 (current active number)
- Service format: 11-8267139
When to Replace
- Threads are stripped, distorted, or will not engage smoothly
- Flats are rounded and the nut can no longer be torqued correctly
- Corrosion is present on the threads or bearing face
- Mounting stud has been replaced and new hardware is required
- Original hardware is damaged during disassembly
Installation Notes
- Inspect the mating stud threads for damage or corrosion before fitting the new nut
- Confirm the thread is 1/4-28 UNF — do not use a 1/4-20 coarse-thread nut
- Thread the nut on by hand first to avoid cross-threading the fine-pitch thread
- On flame-arrestor stud assemblies, confirm the full hardware stack (washers, upper nut, and flame-arrestor seating) before final tightening
- Tighten to the torque specification in the Mercury service manual for the specific assembly
Related Products
Parts Desk Insights
The 1/4-28 fine thread is what makes 8267139 specific — and it’s the most common source of errors when sourcing this nut generically. A 1/4-20 nut looks the same and feels like it threads on for the first turn or two before binding, which can damage the stud. The flame-arrestor mounting stud application is the most common place to see this nut on carbureted MerCruiser engines; if you’re servicing the flame arrestor or carburetor, check the stud and nut condition before reassembly. The superseded number 28941 may still appear on older engine diagrams — 8267139 is the correct current replacement.
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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