Mercury MerCruiser Quicksilver 428611 Brass Pipe Plug — 3/4"-14 NPT
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Mercury MerCruiser Quicksilver 428611 — Brass Pipe Plug, 3/4"-14 NPT
| Part Number | 428611 (service format: 22-428611) |
|---|---|
| Current OEM Replacement | 8M0204679 (22-8M0204679) |
| SKU | 428611 |
| Brand | Mercury / Quicksilver (OEM) |
| Product Type | Brass Pipe Plug (Fitting) |
| Thread | 3/4"-14 NPT (.750-14) |
| Material | Brass |
| Dimensions (pkg) | 1.00" × 1.00" × 0.58" |
| Weight | approx. 60 g (0.13 lb) |
| HTS Code | 741220 |
| Aftermarket Cross-References | Sierra 18-4265 / GLM 21896 / GLM 22032 |
Overview
Mercury 428611 is a genuine OEM brass pipe plug with a 3/4"-14 NPT thread, used across a wide range of Mercury Marine and MerCruiser assemblies including sterndrive transom assemblies, cooling system ports, exhaust components, engine blocks, and jet-drive applications. Mercury parts diagrams identify it as FITTING, Pipe — Brass (.750-14).
Supersession note: 428611 (22-428611) has been superseded to 8M0204679 (22-8M0204679) as the current active Mercury OEM part number. Both numbers refer to the same pipe plug. If your parts diagram or service records show 22-428611, 8M0204679 is the correct current replacement.
Fitment note: This plug appears across many different Mercury and MerCruiser assembly locations. Always confirm the correct application by engine model, serial number, and the exact parts diagram location before ordering. Thread size alone is not sufficient — confirm by the diagram position.
Compatible Applications
- MerCruiser Bravo sterndrive and transom assemblies (confirm serial range and diagram position)
- MerCruiser R / MR / Alpha One transom assemblies (confirm serial range and diagram position)
- MerCruiser 3.0L GM 181 CID I4 — selected assembly positions (confirm serial range)
- MerCruiser 4.3L V6 — selected assembly positions (confirm serial range)
- MerCruiser 5.7L V8 — selected assembly positions (confirm serial range)
- MerCruiser 6.2L — selected assembly positions (confirm serial range)
- MerCruiser 8.1L — selected assembly positions (confirm serial range)
- Mercury Sport Jet — selected assembly positions (confirm serial range)
- Selected Mercury Marine and Mariner applications where parts diagram specifies 428611 / 22-428611 / 8M0204679
- Always confirm by exact engine model, serial number, and diagram position
When to Replace
- Original plug is corroded, rounded, or cannot be removed without damage
- Plug is seeping or leaking at the threaded port
- Plug is damaged during removal and cannot be reinstalled reliably
- Port threads are being retapped or an assembly is being rebuilt — replace the plug as a matter of course
- Proactively during cooling system, exhaust, transom, or drive service where the plug port is accessible
Installation Notes
- Clean the threaded port thoroughly and inspect for corrosion or thread damage before installing the new plug
- Use the correct thread sealant as specified in the Mercury service manual for the exact assembly — some cooling-system and exhaust locations require specific sealants; others specify dry installation
- Do not overtighten — brass pipe plugs are softer than steel and can be damaged or the housing threads can be stripped by excessive torque. Follow the Mercury service manual torque specification for the application
- In cooling system or exhaust applications, run the engine and check for seepage after installation before returning the vessel to service
Technical FAQ
- What is the difference between 428611 and 8M0204679? They are the same pipe plug — 8M0204679 is the current active Mercury OEM part number that supersedes the original 428611. Either number refers to the same 3/4"-14 brass pipe plug.
- Can I use a generic 3/4"-14 brass pipe plug instead? A generic plug of the same thread will fit, but material quality, thread form, and seating geometry can vary. In cooling system and exhaust applications where sealing is critical, using the specified Mercury OEM plug is the safest choice.
- Do I need thread sealant on this plug? It depends on the specific assembly location. Mercury service manuals specify sealant requirements by application — some locations require a specific sealant and others do not. Always follow the service manual for the exact engine, drive, or transom assembly being serviced.
- Why does this plug appear in so many different assemblies? 3/4"-14 NPT is a standard pipe thread size used in many plumbing, cooling, and exhaust ports across Mercury’s product range. The same plug is used wherever a 3/4"-14 pipe port needs to be capped or sealed, regardless of the specific engine or assembly type.
Part Numbers & Cross-References
- Original Mercury: 428611 / 22-428611
- Current Mercury OEM replacement: 8M0204679 / 22-8M0204679
- Aftermarket equivalents: Sierra 18-4265 / GLM 21896 / GLM 22032
Parts Desk Insights
Best Use Case: This plug is the right call whenever a 3/4"-14 port needs to be capped or a damaged original plug needs replacement in a Mercury or MerCruiser application that specifies 428611 or 8M0204679. It’s a small part, but getting the right thread size, material, and OEM specification matters in cooling system and exhaust ports where a failed seal can lead to water intrusion or overheating.
Common Issues: The most frequent problem is overtightening — brass plugs are relatively soft, and too much torque can crack the plug or damage the housing threads, turning a simple replacement into a much bigger job. The second common issue is using the wrong thread sealant — some assembly locations specify a particular sealant and others require a dry fit; always check the service manual for the exact application before applying anything to the threads.
Related Products
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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