Magnetic Drain Plug – Fits Mercury & MerCruiser Outboards & SternDrives (Replaces 8M0058389, 67892A1)
Magnetic Drain Plug – Fits Mercury & MerCruiser Outboards & SternDrives (Replaces 8M0058389, 67892A1) 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
Magnetic Drain Plug – Fits Mercury & MerCruiser Outboards &...
Product Details
This Magnetic Drain Plug – Fits Mercury & MerCruiser Outboards & SternDrives (Replaces 8M0058389, 67892A1) is an essential replacement part for maintaining your lower unit gear case. It is designed to fit all MerCruiser sterndrives (including Alpha One, Alpha One Gen II, MC-1, TR, and TRS models) and most Mercury/Mariner outboards that use a 3/8-16 drain/fill screw, with the exception of the Verado series.
This plug serves as a direct cross-reference for multiple part numbers, including Mercury/QuickSilver 8M0058389, Mercury 67892A1/67892A06/67892A05/14834A1, Sierra 18-2375/18-23751-9, GLM 21731, and Mallory 9-72651.
- Installs easily as a threaded plug with a pre-installed seal.
- The magnetic tip captures harmful ferrous metal particles, helping to prevent premature gear wear and damage.
- Engineered for use as both the lower unit gear lube drain and fill hole screw.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury/QuickSilver | 8M0058389 |
| Mercury | 67892A1 |
| Mercury | 67892A06 |
| Mercury | 67892A05 |
| Mercury | 14834A1 |
| Sierra | 18-2375 |
| Sierra | 18-23751-9 |
| GLM | 21731 |
| Mallory | 9-72651 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For MerCruiser Sterndrives: This plug fits all sterndrive models using a 3/8-16 drain/fill hole screw for the lower unit gear lube.
| Brand | Model | Years | OEM Part No. | Notes |
|---|---|---|---|---|
| MerCruiser | Alpha One | All | 8M0058389 | Lower unit gear lube drain/fill hole |
| MerCruiser | Alpha One Gen II | All | 8M0058389 | Lower unit gear lube drain/fill hole |
| MerCruiser | MC-1 | All | 8M0058389 | Lower unit gear lube drain/fill hole |
| MerCruiser | TR | All | 8M0058389 | Lower unit gear lube drain/fill hole |
| MerCruiser | TRS | All | 8M0058389 | Lower unit gear lube drain/fill hole |
| MerCruiser | I | All | 8M0058389 | Lower unit gear lube drain/fill hole |
| MerCruiser | R | All | 8M0058389 | Lower unit gear lube drain/fill hole |
| MerCruiser | MR | All | 8M0058389 | Lower unit gear lube drain/fill hole |
Technical Specs
- Product Type
- Magnetic Oil Drain Plug
- Installation
- Threaded plug with pre-installed seal
- Connection
- 3/8-16 UNC thread
- Housing Material
- Metal with magnetic element
- Housing Color
- Chrome/Silver
- Fitting Type
- Threaded plug with seal
- Thread Size
- 3/8-16 UNC
- Other Technical Attributes
- Magnetic plug design captures ferrous metal particles to prevent gear damage
What’s in the Box
- 1 x Lower Unit Gear Lube Drain and Fill Hole Screw with Seal (Replaces 8M0058389)
Installation Notes
- Ensure the engine is off and the drive unit is in a position that allows for complete draining. Place a suitable drain pan under the lower unit.
- Using a large flathead screwdriver, carefully remove the lower (drain) and upper (vent) plugs.
- Allow the gear lube to drain completely. Inspect the old lube for any signs of water intrusion (milky appearance) or excessive metal shavings.
- Clean the sealing surfaces around the drain and vent holes on the gear case.
- Install the new magnetic drain plug in the lower hole. Tighten it firmly, but do not overtighten to avoid stripping the threads.
- Pump new, manufacturer-recommended gear lube into the lower hole until it begins to flow out of the upper vent hole.
- Re-install the upper vent plug and tighten securely.
- Remove the lube pump nozzle and quickly install and tighten the lower drain plug.
- Wipe the drive unit clean and check for any leaks around the plugs after a few minutes.
Troubleshooting & FAQ
Which MerCruiser sterndrives does this plug fit?
This magnetic drain plug is compatible with all MerCruiser sterndrives that utilize a 3/8-16 UNC threaded screw for the gear lube drain and fill holes. This includes popular models like Alpha One (Gen I & II), MC-1, R, MR, TR, and TRS drives.
Will this fit my Mercury or Mariner outboard?
It fits a wide range of Mercury and Mariner outboards equipped with a 3/8-16 drain/fill screw. However, it is not compatible with the Verado series. Always verify the part number or thread size of your existing plug before ordering.
How does the magnetic feature work?
The tip of the plug contains a strong magnet that attracts and holds onto any fine metallic particles (ferrous debris) circulating in the gear lube. This prevents the particles from causing accelerated wear or damage to sensitive gear sets and bearings.
What is the thread size of this plug?
The plug has a 3/8-16 UNC thread, which is a common standard for many Mercury and MerCruiser gear cases.
How often should I inspect or replace the plug and seal?
The plug itself is durable, but the seal should be replaced at every gear lube change to ensure a watertight fit. Inspect the magnet for metal shavings at each service interval; a small amount of fine fuzz is normal, but larger chips may indicate an internal issue.
What are the signs of a leaking or failing drain plug?
Signs include visible gear lube drips from the drain hole, a low gear lube level, or water intrusion into the gear case (which makes the oil appear milky or creamy). A damaged seal or stripped threads are common causes of failure.
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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