Lower Unit Drain Plug Gearcase Screw with Seal, 2-Pack – Fits Mercury, MerCruiser & Mariner
Lower Unit Drain Plug Gearcase Screw with Seal, 2-Pack – Fits Mercury, MerCruiser & Mariner is backordered and will ship as soon as it is back in stock.
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Lower Unit Drain Plug Gearcase Screw with Seal, 2-Pack – Fits Mercu...
Lower Unit Drain Plug Gearcase Screw with Seal, 2-Pack – Fits Mercury, MerCruiser & Mariner is backordered and will ship as soon as it is back in stock.
Product Details
This 2-pack of non-magnetic lower unit drain plug gearcase screws with seals is designed for Mercury and Mariner outboards equipped with a 3/8-16 drain and fill hole. The screws are also used with many MerCruiser stern-drive applications. Verify the thread size, plug style, and original part number before ordering, especially for Verado and other model-specific applications.
These aftermarket replacement screws are listed as cross-references for Mercury 10-79953Q04, 10-79953A2, 10-79953Q2, 18-2244, and 22420, as well as selected Johnson/Evinrude, Mallory, and Chrysler/Force/US Marine references shown below. Cross-reference numbers are provided for identification and should be checked against the original component.
- Non-magnetic metal construction for corrosion resistance in marine service.
- 3/8-16 threaded design with an included sealing gasket on each screw.
- Suitable for routine lower-unit gear-lubricant service when the application is confirmed.
- Two drain plug screws are included in the package.
Part Number Matrix
Use this matrix as a cross-reference guide. Confirm the original part number and application before installation.
| Brand | Part Number |
|---|---|
| Mercury | 10-79953Q04 |
| Mercury | 10-79953A2 |
| Mercury | 10-79953Q2 |
| Mercury | 18-2244 |
| Mercury | 22420 |
| Johnson/Evinrude | 307552 |
| Mallory | 60101 |
| Mallory | 60102 |
| Chrysler/Force/US Marine | 19183 |
| Chrysler/Force/US Marine | F50556 |
| Chrysler/Force/US Marine | F8077 |
| Chrysler/Force/US Marine | F8186 |
Engine & Model Compatibility
The applications below are reference guidance for models reported with the listed drain-plug references. Compatibility depends on the exact engine or drive configuration, year, serial range, and lower-unit design. Confirm your specific model and original plug before purchase.
| Brand | Model or Application | Rated HP | Stroke | Reference | Notes |
|---|---|---|---|---|---|
| Mercury/MerCruiser | MerCruiser I, R, MR, Alpha One, TR, and TRS drive applications | 10-79953Q04 | Verify drive version and plug specification. | ||
| Mercury | Outboards using a 3/8-16 drain hole | 40–250 | 10-79953Q04 | Verify the exact model; do not assume fitment from horsepower alone. | |
| Mercury | 40, 50, 60, and Jet 40 EFI | 40–60 | 4-Stroke | 10-79953Q04 | Reported for applicable 4-cylinder configurations. |
| Mercury | 30/40 EFI | 30–40 | 4-Stroke | 10-79953Q04 | Reported for applicable 3-cylinder configurations. |
| Mercury | VAZER | 4-Stroke | 10-79953Q04 | Verify the exact drive application. | |
| Mercury | 75, 80, 90, and 115/125 DFI | 75–125 | 10-79953Q04 | Reported for applicable 1.5L configurations. | |
| Mercury | 115 Pro XS | 115 | 10-79953Q04 | Verify model year and serial range. | |
| Mercury | 135, 150, and 175 DFI | 135–175 | 10-79953Q04 | Reported for applicable 2.5L configurations. | |
| Mercury | 150, 175, and 200 Pro XS | 150–200 | 10-79953Q04 | Reported for applicable 2.5L configurations. | |
| Mercury | 225 and 250 Pro XS | 225–250 | 10-79953Q04 | Reported for applicable 3.0L DFI configurations. | |
| Mercury | 200 DFI Jet Drive | 200 | 10-79953Q04 | Verify lower-unit application. | |
| Mercury | 540 Stroker 4V | 10-79953Q04 | Verify the specific performance application. | ||
| Mariner | Outboards using a 3/8-16 drain hole | Verify the original plug and model-specific requirements. | |||
| Johnson/Evinrude | Applications using the referenced drain plug | 307552 | Confirm the original part number. | ||
| Chrysler/Force/US Marine | Applications using the referenced drain plug | 19183, F50556, F8077, F8186 | Confirm the original part number. |
Technical Specs
- Product Type
- Lower unit drain/fill plug screws with sealing gaskets
- Quantity
- 2 screws with seals
- Installation
- Manual installation with a suitable large flat-blade screwdriver
- Thread Size
- 3/8-16
- Material
- Non-magnetic metal, listed as stainless steel
- Color
- Silver/metallic
- Fitting Type
- Threaded drain/fill plug with sealing gasket
What's in the Box
- 2 x lower unit drain plug gearcase screws
- 2 x sealing gaskets, one for each screw
Installation Notes
- Place a suitable drain pan beneath the lower unit drain screw.
- Using a large flat-blade screwdriver, remove the old drain plug and allow the gear lubricant to drain.
- Inspect the old lubricant for water contamination, a milky appearance, or metal particles.
- Clean the drain-hole threads and sealing surface.
- Install one new drain plug screw with its sealing gasket. Start the screw by hand to prevent cross-threading.
- Tighten it securely according to the engine or drive manufacturer's service instructions. Do not overtighten.
- Remove the upper vent screw and refill the lower unit with the specified gear lubricant if performing a lubricant change.
- Reinstall the vent screw, clean away excess lubricant, and check the drain plug for leaks.
Troubleshooting & FAQ
How do I confirm fitment?
Compare the original screw, thread size, sealing arrangement, and part number with the information above. Model name or horsepower alone is not sufficient because lower-unit configurations can vary by year, serial range, and drive version.
Is this plug magnetic?
No. This listing describes a non-magnetic plug. If your original component uses a magnetic feature or a different head style, verify the replacement before installation.
Should the seal be replaced during gear-lubricant service?
Replacing the sealing gasket during each lubricant change is common service practice. Inspect the screw threads, head, and sealing surface and replace the screw if damaged or corroded.
What indicates a sealing problem?
Gear-lubricant leakage around the drain screw or a milky appearance in the lubricant can indicate water intrusion or a damaged sealing surface. Stop use and investigate the cause before returning the unit to service.
Is this an OEM component?
This listing is for an aftermarket replacement. The reference numbers are provided for cross-reference and identification only.
Can both screws be installed at the same time?
The package contains two screws. Install only the number required by your service procedure and keep the additional screw as a spare if appropriate.
Safety & Important Information
- Verify the original part number, thread size, head style, and sealing arrangement before ordering.
- Do not rely on horsepower alone to determine fitment.
- Follow the engine or sterndrive manufacturer's service instructions for lubricant type, filling procedure, and tightening requirements.
- Professional installation is recommended if you are unfamiliar with lower-unit service.
About Sea Sierra
- Pro-Grade Standards — Marine replacement parts selected for dependable service in real-world conditions.
- Fast Global Fulfillment — Standard delivery options are available for many regions.
- Manufacturer-Direct Value — Practical replacement parts at competitive pricing.
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