Lower Unit Drain Plug Seal Gasket – Fits Mercury/MerCruiser Outboard/Sterndrive (Replaces 12-19183-3)

Lower Unit Drain Plug Seal Gasket – Fits Mercury/MerCruiser Outboard/Sterndrive (Replaces 12-19183-3)

This high-quality oil drain plug seal gasket is designed for Mercury/MerCruiser outboard and sterndrive engines that use a 3/8-16 drain/fill screw in the gearcase. It provides a secure, leak-free seal to keep gear oil in and water out, protecting your engine's lower unit components.

It serves as 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; Mallory 9-60101 and 9-60102; and others.

• Material: Made from a high-quality, non-asbestos sealing material that is oil-resistant and impermeable.
• Function: Creates a reliable seal for outdrive drain plugs, vent plugs, and oil level screws.
• Package Includes: A bulk pack of 10 gaskets, ensuring you have replacements ready for multiple services.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Mercury owners, here’s a guide to help you identify your engine’s serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

For Johnson/Evinrude owners, here’s a guide to help you identify your engine’s serial/model: Johnson Serial Number Guide.

For Tohatsu models, confirm your engine model/year in the table below.

Mercury/Mariner/MerCruiser Applications

Other Compatible Applications

Technical Specifications

Package Contents

• 10 x Lower Unit Drain Plug Seal Gaskets (Replaces 12-19183-3 / 12-19183Q02 / 12-19183K02)

Installation Guide

1. Position a drain pan under the lower unit of your engine.
2. Locate and remove the lower drain/fill screw and the upper vent screw.
3. Allow the old gear oil to drain completely from the gearcase.
4. Inspect the magnetic tip of the drain screw and the old oil for metal shavings or a milky (water-contaminated) appearance, which can indicate internal issues.
5. Thoroughly clean the screw threads and the sealing surface on the gearcase.
6. Remove and properly discard the old seal gasket from the drain screw.
7. Place the new seal gasket onto the drain screw.
8. Insert the nozzle of your gear lube pump into the lower drain hole and pump in fresh lubricant until it begins to flow out of the upper vent hole.
9. Reinstall the upper vent screw with its gasket first to create a vacuum, which helps prevent lube from spilling.
10. Quickly remove the lube nozzle and reinstall the lower drain/fill screw with its new gasket.
11. Tighten both screws to the manufacturer's recommended torque. Do not overtighten, as this can damage the gasket or threads.
12. Wipe the area clean and check for any leaks after a short period.

Troubleshooting & FAQ

Q: How do I know if this gasket will fit my engine's drain screw?

A: This gasket is specifically designed for drain/fill screws with a 3/8-16 thread size. It fits a wide range of Mercury/MerCruiser outboards and sterndrives, plus select Tohatsu and Johnson/Evinrude models. The best way to confirm is to check your engine's service manual or the old screw itself. You can also use the part number cross-reference and compatibility tables on this page.

Q: How often should I replace this drain plug seal?

A: The drain plug seal is a single-use item and must be replaced every time you change your lower unit gear oil. Reusing an old gasket can lead to an improper seal, causing gear oil leaks and allowing water to enter the gearcase, which can lead to catastrophic failure.

Q: I've installed the new gasket, but my lower unit is still leaking oil. What could be the cause?

A: If a leak persists with a new gasket, first check that the drain screw is tightened to the correct torque specification—not too loose, and not overtightened. Next, carefully inspect the sealing surfaces on both the screw and the gearcase for any nicks, deep scratches, or old gasket material. A damaged or dirty surface will prevent even a new gasket from sealing correctly.

Q: OEM vs. Aftermarket?

A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

Q: How fast do you ship and how much does it cost?

A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

Q: What is your warranty and return policy?

A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.