Lower Unit Drain Plug Seal Gasket – Fits Mercury/MerCruiser Outboard/Sterndrive (Replaces 12-19183-3, 12-19183Q02, 12-19183K02)
Lower Unit Drain Plug Seal Gasket – Fits Mercury/MerCruiser Outboard/Sterndrive (Replaces 12-19183-3, 12-19183Q02, 12-19183K02) 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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Lower Unit Drain Plug Seal Gasket – Fits Mercury/MerCruiser Outboar...
Product Details
This Lower Unit Drain Plug Seal Gasket is engineered for a precise fit on Mercury/MerCruiser outboard and sterndrive engines that use 3/8-16 drain or fill screws in the gearcase. It covers a wide range of models and years, providing a reliable seal to prevent gear oil leakage.
This part is a direct replacement for multiple OEM and aftermarket part numbers, including Mercury 12-19183-3, 12-19183Q02, and 12-19183K02; Sierra 18-2244 and 18-2945; and Mallory 9-60101.
- Designed for single-use application with each gear lube change to ensure a perfect seal.
- Made from high-quality, oil-resistant, and impermeable sealing material.
- Prevents water intrusion and protects internal gearcase components from corrosion.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 12-19183-3 |
| Mercury | 12-19183Q02 |
| Mercury | 12-19183K02 |
| Sierra | 18-2244 |
| Sierra | 18-2945 |
| SEI | 98-102-09 |
| Mallory | 9-60101 |
| Mallory | 9-60102 |
| GLM | 31170 |
| Red Rhino | MR-103 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
Compatible with most Mercury, Mariner, and MerCruiser models utilizing a 3/8-16 drain plug. Note that it is not compatible with models manufactured in Japan.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | Non-Japanese Outboards | Multiple | Both | Multiple | 12-19183-3 | Compatible with most Mercury/Mariner outboard models except Japanese-made models |
| MerCruiser | All Models | Multiple | Both | Multiple | 12-19183-3 | Compatible with all MerCruiser sterndrive models |
| Mercury | Mariner Outboards | Multiple | Both | Multiple | 12-19183-3 |
Technical Specs
- Product Type
- Oil Drain Plug Seal Gasket
- Installation
- Fits 3/8-16 drain/fill screw holes in outboard and sterndrive gearcases
- Material
- High-quality non-asbestos sealing material
- Color
- Black
- Dimensions
- Outside diameter: 14.2 mm (0.56 inch), Inner diameter: 9 mm (0.35 inch)
- Thread Size
- 3/8-16
- Application
- Outdrive drain, vent plug, oil level use
- Function
- Prevents gear oil leakage, keeps oil in and water out
- Replacement
- Single-use item, should be replaced with each oil change
- Other Technical Attributes
- Oil-resistant, impermeable
What’s in the Box
- 10 x Lower Unit Drain Plug Seal Gaskets (12-19183-3/12-19183Q02/12-19183K02)
Installation Notes
- Position a suitable drain pan under the lower unit.
- Remove the lower magnetic drain plug screw and old gasket. Inspect the magnet for metal shavings.
- Remove the upper gearcase vent screw to allow air to enter.
- Let the gear lube drain completely from the lower unit.
- Clean the threads of both the drain plug and vent screw openings.
- Place the new seal gasket onto the lower magnetic drain plug screw.
- Fill the gearcase with the recommended lubricant through the bottom hole until it flows out of the top vent hole.
- Reinstall the upper vent screw first, then reinstall the lower drain plug screw with the new gasket. Do not overtighten.
Troubleshooting & FAQ
How do I know if this gasket will fit my engine?
This gasket fits most Mercury and MerCruiser outboards and sterndrives with 3/8-16 drain screw holes. It does not fit Mercury/Mariner models made in Japan. Always verify your part number or check your service manual to confirm compatibility.
Can I reuse this gasket?
No. These are single-use gaskets designed to compress and form a tight seal once. Reusing a crushed gasket will likely lead to a gear oil leak and potential water intrusion.
What are the signs of a failing drain plug gasket?
A milky or creamy appearance in your gear lube is a primary sign of water intrusion, often caused by a failed gasket. You may also notice gear oil weeping from the drain screw.
What's the difference between this and the OEM gasket?
Our gasket is manufactured from a high-quality, oil-resistant non-asbestos material designed to meet or exceed OEM specifications for fit, seal, and durability, offering comparable performance at a better value.
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.
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