Marine Lower Unit Oil Drain Plug – Fits Mercury/Mercruiser 40–115 HP (Replaces 10-79953Q2, 10-79953A2, 18-2244)
Marine Lower Unit Oil Drain Plug – Fits Mercury/Mercruiser 40–115 HP (Replaces 10-79953Q2, 10-79953A2, 18-2244) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
U.S. orders usually arrive within 6–15 days, depending on stock location and destination.
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Marine Lower Unit Oil Drain Plug – Fits Mercury/Mercruiser 40–115 H...
Marine Lower Unit Oil Drain Plug – Fits Mercury/Mercruiser 40–115 HP (Replaces 10-79953Q2, 10-79953A2, 18-2244) is backordered and will ship as soon as it is back in stock.
Product Details
This Marine Lower Unit Oil Drain Plug is an aftermarket replacement for selected Mercury and Mercruiser outboard gearcases. It is intended for applications using a 3/8-16 drain-plug thread and is listed for Mercury/Mercruiser outboards in the 40–115 HP range. Match the original plug, thread size, and manufacturer reference before ordering.
This drain plug cross-references manufacturer and aftermarket references including Mercury 10-79953Q2, 10-79953A2, 10-79953Q04, and 10-79953, as well as Sierra 18-2244. Catalog references also associate GLM 22420 with Mercury 10-79953Q2.
- Direct replacement drain screw for compatible lower-unit gearcases.
- 3/8-16 thread for the applications listed below.
- Durable stainless-steel construction with a non-magnetic design.
- Supplied as one replacement drain plug with one gasket seal.
Part Number Matrix
Use the following references to compare the original part with this replacement. Number references are not a substitute for confirming the complete engine model and serial-number application.
| Brand | Part Number | Reference Type |
|---|---|---|
| Mercury | 10-79953Q2 | OEM reference |
| Mercury | 10-79953A2 | OEM reference |
| Mercury | 10-79953Q04 | OEM reference |
| Mercury | 10-79953 | OEM reference |
| Mercury | 79953Q04 | Reference number |
| Sierra | 18-2244 | Aftermarket reference |
| GLM | 22420 | Aftermarket reference |
| Mallory | 9-72650 | Aftermarket reference |
| Easterner | C14406 | Aftermarket reference |
| WSM | 607-14 | Aftermarket reference |
Engine & Model Compatibility
The available product record lists this replacement for Mercury/Mercruiser outboards from 40 to 115 HP. Exact fitment can vary by model, year, gearcase, and serial-number range, so verify your original part number and drain-plug thread before purchase.
| Brand | Application | Rated HP | Compatible Reference |
|---|---|---|---|
| Mercury | Outboard | 40 | 10-79953Q2 / 10-79953A2 |
| Mercury | Outboard | 50 | 10-79953Q2 / 10-79953A2 |
| Mercury | Outboard | 60 | 10-79953Q2 / 10-79953A2 |
| Mercury | Outboard | 70 | 10-79953Q2 / 10-79953A2 |
| Mercury | Outboard | 75 | 10-79953Q2 / 10-79953A2 |
| Mercury | Outboard | 90 | 10-79953Q2 / 10-79953A2 |
| Mercury | Outboard | 115 | 10-79953Q2 / 10-79953A2 |
| Mercruiser | Compatible lower-unit application where the original plug matches | Not specified | 10-79953Q2 / 10-79953A2 |
Technical Specs
- Product Type
- Lower Unit Oil Drain Plug
- Installation
- Direct replacement drain screw with gasket
- Thread Size
- 3/8-16
- Material
- Stainless steel
- Color
- Silver
- Magnetic Design
- Non-magnetic
- Product Quantity
- One drain plug
What’s in the Box
- 1 x Lower Unit Oil Drain Plug
- 1 x Gasket Seal
Installation Notes
- Position a suitable drain pan under the lower unit gearcase.
- Remove the upper vent plug and lower drain plug with a correctly sized large flathead screwdriver.
- Allow the gear oil to drain completely. Inspect the old oil for metal particles or a milky appearance, which may indicate internal wear or water intrusion.
- Clean the gearcase opening and inspect the threads before installation.
- Install the replacement drain plug with the supplied gasket. Start it by hand, then tighten it securely without overtightening.
- Pump new marine gear lubricant into the lower opening until lubricant flows from the upper vent opening.
- Install the vent plug with its gasket, then remove the lubricant pump and promptly reinstall the lower drain plug.
- Wipe the gearcase clean and check for leakage after servicing.
Troubleshooting & FAQ
How do I confirm this plug fits my engine?
Compare your original drain plug with the listed references and confirm the 3/8-16 thread. Also verify the complete engine model, year, gearcase, and serial-number range because horsepower alone does not establish fitment.
Is this plug magnetic?
No. This replacement uses a non-magnetic stainless-steel design. If your original plug is magnetic or has a different shape, confirm the application before ordering.
What are the signs of a faulty drain plug or gasket?
Common signs include gear-oil leakage around the plug, a damaged or brittle gasket, damaged threads, or a plug that will not tighten correctly. Replace the gasket whenever the gear oil is serviced.
How often should the gasket be replaced?
Replace the gasket whenever the drain plug is removed or the gear oil is changed. Follow the service interval specified in your engine or sterndrive manual.
Is this an OEM part?
This is an aftermarket replacement, not a genuine Mercury OEM component. The listed OEM and aftermarket numbers are provided as application references only.
What are the shipping speed and cost?
Typical transit is 5–15 days. Standard shipping is free, with expedited options shown at checkout where available.
What is the warranty and return policy?
This product is covered by a 1-year warranty against manufacturing defects under normal use. Returns are accepted within the standard return window for unused items in their original condition. Contact support for return instructions.
Safety & Important Information
- Verify the original part number, thread size, dimensions, and application before purchase.
- Do not rely on horsepower alone to determine compatibility.
- This is an aftermarket replacement part, not an OEM component.
- Use the lubricant type and tightening procedure specified by the engine manufacturer.
- Professional installation is recommended if the gearcase threads or sealing surface are damaged.
About Sea Sierra
- Pro-Grade Standards — We supply marine replacement parts designed for dependable service in real-world operating conditions.
- Fast Global Fulfillment — Free standard delivery is available to most regions, with typical transit of 5–15 days.
- Manufacturer-Direct Value — We focus on practical replacement parts and consistent quality at a fair price.
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