Lower Unit Drain Plug Gasket – Fits Mercury, MerCruiser, Evinrude & Johnson (Replaces Mercury 12-19183-3, Sierra 18-2244)
Lower Unit Drain Plug Gasket – Fits Mercury, MerCruiser, Evinrude & Johnson (Replaces Mercury 12-19183-3, Sierra 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
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Lower Unit Drain Plug Gasket – Fits Mercury, MerCruiser, Evinrude &...
Lower Unit Drain Plug Gasket – Fits Mercury, MerCruiser, Evinrude & Johnson (Replaces Mercury 12-19183-3, Sierra 18-2244) is backordered and will ship as soon as it is back in stock.
Product Details
This Lower Unit Drain Plug Gasket helps seal the gearcase drain and fill screw to reduce lubricant leaks and water intrusion. It is an aftermarket replacement gasket for marine applications using a compatible 3/8-16 drain/fill screw. The gasket is listed for a wide range of Mercury, MerCruiser, Evinrude, Johnson, and Tohatsu applications; always verify the screw size, original gasket, and exact engine or sterndrive application before ordering.
The gasket corresponds to Mercury part numbers 12-19183, 12-19183-3, and 12-19183Q02. Additional aftermarket references commonly associated with this gasket include Sierra 18-2244, GLM 31170, SEI 98-102-09, Mallory 9-60101, and OBR Red Rhino MR-103. GLM catalog information identifies GLM 31170 as a gasket corresponding to Mercury 12-19183-3 and specifies the gasket-only item.
- Installs between the drain or fill screw head and the gearcase housing.
- Designed for use with compatible 3/8-16 drain/fill screws.
- Oil-resistant sealing material is suitable for lower-unit gear lubricant service.
- Replace the gasket during each lower-unit gear-lubricant change instead of reusing the old seal.
Part Number Matrix
Use the following references to compare the gasket with the part removed from your gearcase. Number cross-references are provided for identification and do not replace application verification.
| Brand | Part Number |
|---|---|
| Mercury | 12-19183 |
| Mercury | 12-19183-3 |
| Mercury | 12-19183K02 |
| Mercury | 12-19183Q02 |
| Sierra | 18-2244 |
| Sierra | 18-2945 |
| SEI | 98-102-09 |
| Mallory | 9-60101 |
| Mallory | 9-60102 |
| GLM | 31170 |
| OBR Red Rhino | MR-103 |
Engine & Model Compatibility
Fitment depends on the drain/fill screw and gearcase design. Confirm the exact engine or sterndrive model, year, serial range, and screw size where applicable. The following applications are reference categories rather than confirmation for every model in a brand or horsepower range.
| Brand | Application | Rated HP | Stroke | Years | Reference | Fitment Condition |
|---|---|---|---|---|---|---|
| Mercury | Outboards | 25–400 | 2- & 4-Stroke | Various | 12-19183-3 | Use only where the engine uses the compatible 3/8-16 drain/fill screw; Japanese-origin models may use different parts. |
| Mariner | Outboards | 25–400 | 2- & 4-Stroke | Various | 12-19183-3 | Verify the original gasket and screw size; Japanese-origin models may use different parts. |
| MerCruiser | Sterndrives | Various | Not applicable | Various | 12-19183-3 | For applications using the compatible 3/8-16 drain/fill screw. GLM lists the corresponding gasket-only item for MerCruiser-related catalog use. |
| Evinrude | Outboards | Various | Various | Various | Application dependent | Verify that the original drain/fill screw and gasket match the 3/8-16 application. |
| Johnson | Outboards | Various | Various | Various | Application dependent | Verify that the original drain/fill screw and gasket match the 3/8-16 application. |
| Tohatsu | Outboards | Various | Various | Various | Application dependent | Confirm the screw thread, gasket dimensions, and original part before ordering. |
Technical Specs
- Product Type
- Lower Unit Drain Plug Gasket / Seal Washer
- Installation Position
- Between the drain/fill screw and the gearcase housing
- Compatible Screw Type
- 3/8-16 drain/fill screw applications
- Fitting Type
- Gasket / sealing washer
- Material
- Oil-resistant sealing material; compare the replacement with the original gasket before installation
- Color
- Blue
- Approximate Dimensions
- Inner diameter: approximately 9 mm (0.35 in)
Outer diameter: approximately 14 mm (0.55 in)
Thickness: approximately 1.5 mm (0.06 in) - Application Note
- Not intended for Japanese-origin Mercury or Mariner applications that use a different drain-plug gasket.
What’s in the Box
This listing is for the gasket-only product. Quantity options may vary by the selected package; choose the quantity shown on the product option or order confirmation.
- 10 x Lower Unit Drain Plug Seal Gasket
- 12 x Lower Unit Drain Plug Seal Gasket
- 15 x Lower Unit Drain Plug Seal Gasket
- 20 x Lower Unit Drain Plug Seal Gasket
Important: The drain screw, gear-lubricant pump, and other service parts are not included unless specifically shown in the selected package option.
Installation Notes
- Place a suitable oil drain pan under the lower unit.
- Remove the lower drain/fill screw from the gearcase.
- Remove the upper-level or vent screw so air can enter and the lubricant can drain completely.
- Inspect the magnetic tip of the drain screw for unusual metal shavings.
- Remove and discard the old gasket from the screw.
- Clean the screw, threads, and gasket seating surface on the gearcase.
- Compare the new gasket with the old one and slide the new gasket onto the drain screw.
- After the lubricant has drained, reinstall the lower drain screw and tighten it to the manufacturer's specified torque. Do not overtighten.
- Using a gear-lube pump, fill the gearcase through the lower drain hole until fluid emerges from the upper vent hole.
- Reinstall the upper vent screw, then quickly remove the pump filler tube and reinstall the lower drain screw with its new gasket.
- Check for leaks after servicing and again after the first short operating period.
Troubleshooting & FAQ
How often should I replace this drain screw gasket?
Replace the gasket whenever you change the lower-unit gear lubricant. Reusing a compressed or damaged gasket can allow lubricant to leak out and water to enter the gearcase.
Will this gasket fit my engine?
It is intended for compatible applications using a 3/8-16 drain/fill screw and is commonly cross-referenced to Mercury 12-19183-3. Confirm the exact model, year, serial range, original gasket, and screw size before ordering. Japanese-origin Mercury and Mariner models may require a different gasket.
Is the drain plug included?
No. This is a gasket-only product. The drain or fill screw and other service equipment are not included unless specifically identified in the selected package option.
What are the signs of a failing drain plug gasket?
Common signs include gear lubricant leaking around the drain screw, a low lubricant level, or milky or cloudy lubricant caused by water contamination. Investigate promptly to help prevent gearcase damage.
Is this an OEM part?
No. This is an aftermarket replacement gasket. Mercury 12-19183-3 and the other numbers listed above are manufacturer or aftermarket reference numbers used for identification and comparison.
How quickly will my order ship?
Typical international transit is 5–15 days. Standard shipping is free where offered, and expedited options appear at checkout when available.
What warranty and return coverage applies?
The product is covered by a 1-year warranty against manufacturing defects under normal use. Returns are accepted within the applicable standard return window when the item is unused and in its original condition. Contact support with your order details for assistance.
Safety & Important Information
- Verify the original gasket, screw thread, dimensions, and exact engine or sterndrive application before purchase.
- Do not rely on horsepower or brand alone to confirm fitment.
- This is an aftermarket replacement, not an OEM component.
- Use the manufacturer's service manual for torque specifications and gear-lubricant procedures.
- Professional installation is recommended when you are unsure of the correct application or service procedure.
About Sea Sierra
- Pro-Grade Standards — We supply marine replacement parts selected for dependable service in real-world conditions.
- Fast Global Fulfillment — Free standard delivery is available to most regions, with typical transit of 5–15 days.
- Manufacturer-Direct Value — Fair pricing with attention to material selection and quality control.
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