Drain Screw – Fits Mercury/Mariner Outboards & MerCruiser Stern Drives (Replaces 10-79953, 10-79953A2)
Drain Screw – Fits Mercury/Mariner Outboards & MerCruiser Stern Drives (Replaces 10-79953, 10-79953A2) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Drain Screw – Fits Mercury/Mariner Outboards & MerCruiser Stern...
Product Details
This high-quality Drain Screw – Fits Mercury/Mariner Outboards & MerCruiser Stern Drives serves as a crucial replacement for maintaining your gear case. It is designed for broad compatibility, fitting most Mercury/Mariner outboards and MerCruiser stern drives (including I, R, MR, Alpha One, TR, and TRS series) that use a 3/8-16 drain screw. It also fits various Chrysler, Force, and US Marine models with the same thread specification, excluding the Mercury Verado series.
This part provides a direct interchange for multiple OEM and aftermarket numbers, including Mercury 10-79953, 10-79953A2, 10-79953Q04, Sierra 18-2244, and GLM 22420, ensuring a precise fit and reliable function.
- Constructed from durable, corrosion-resistant, non-magnetic stainless steel.
- Installs easily with a standard hex head tool, requiring only hand-tightening.
- Package includes three replacement gaskets to ensure a leak-proof seal.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 10-79953 |
| Mercury | 10-79953A2 |
| Mercury | 10-79953Q04 |
| Mercury | 10-79953Q2 |
| Mercury | 10-20259 |
| Mercury | 10-28634 |
| Mercury | 10-28634A1 |
| Chrysler/Force | 10-F50109 |
| Chrysler/Force | F40109 |
| GLM | 22420 |
| Mallory | 9-72650 |
| Sierra | 18-2244 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Mercury and MerCruiser engines, this screw fits a wide variety of outboards and stern drives with 3/8-16 drain plugs, with the notable exception of the Verado series.
For Chrysler and Force applications, compatibility is confirmed for models utilizing the 3/8-16 thread size.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury Marine | All Outboards | Various | 2-Stroke & 4-Stroke | Various | 10-79953, 10-79953A2 | Except Verado series |
| MerCruiser | All Stern Drives | Various | 4-Stroke | Various | 10-79953, 10-79953A2 | I, R, MR, Alpha One, TR, TRS series |
| Chrysler/Force | Various | Various | 2-Stroke | Various | 10-79953, 10-F50109, F40109 | For models with 3/8-16 drain screws |
Technical Specs
- Product Type
- Gear Case Drain Screw
- Material
- Stainless steel (non-magnetic)
- Thread Size
- 3/8"-16 UNC
- Fitting Type
- Hex head
- Connection
- 3/8-16 threaded
- Finish
- Silver/metallic
- Other Attributes
- Non-magnetic design
What’s in the Box
- 1 x Gear Case Drain Screw (equivalent to 10-79953Q04)
- 3 x Drain Screw Gaskets (equivalent to 26-830749)
Installation Notes
- Place a suitable drain pan under the lower unit of your engine.
- Locate and remove the old gear lube drain screw using a properly sized wrench. Have cleaning cloths ready for drips.
- Allow all old gear lubricant to drain completely. Inspect the old lube for metal shavings or water, which may indicate other issues.
- Wipe the area around the drain plug hole clean to ensure a good sealing surface.
- Place one of the new gaskets on the new drain screw.
- Thread the new screw into the drain hole and tighten it securely by hand. Do not overtighten, as this can damage the gear case threads or the screw.
Troubleshooting & FAQ
How do I know if this drain screw fits my engine?
This screw fits most Mercury/Mariner outboards (except Verado), MerCruiser stern drives, and Chrysler/Force models that use a 3/8"-16 thread. Please verify your engine's service manual or compare your existing screw's thread size to be certain. Our compatibility tables provide a general guide.
Why is a non-magnetic screw important?
While some OEM drain screws are magnetic to catch metal particles, non-magnetic stainless steel offers superior corrosion resistance, which is critical in marine environments. It ensures the screw will not rust or seize in the gear case, making future fluid changes easier.
How often should I replace the drain screw and gasket?
The drain screw gasket should be replaced every time you change your gear lube to ensure a proper seal. The screw itself does not have a fixed replacement interval but should be replaced if the hex head becomes stripped or if there is any visible damage to the threads.
What are the signs of a failing drain screw or gasket?
The most common sign is a leak of gear lube from the drain plug area. You may see an oily sheen on the water or notice the lube level is low. A stripped screw head or corroded screw are also clear indicators that a replacement is needed.
Is a new gasket required with every oil change?
Yes, it is highly recommended. The gasket compresses to create a tight seal. Reusing an old gasket can lead to leaks, as it may not seal properly a second time. This kit includes three gaskets for your convenience.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
Payment & Security
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