Gearcase Drain Plug Seal – Fits Mercury/Mariner/MerCruiser Marine Engines (Replaces 26-830749, 8M0204693)

Gearcase Drain Plug Seal – Fits Mercury/Mariner/MerCruiser Marine Engines (Replaces 26-830749, 8M0204693)

This gearcase drain plug seal is designed for use with a wide range of Mercury/Mariner outboard engines and MerCruiser sterndrive units. It functions as a critical sealing washer for the gearcase drain and fill plugs, preventing gear oil leakage from the lower unit and protecting it from water intrusion.

This component is a direct replacement for Mercury OEM parts 26-830749 and 8M0204693. It also replaces Sierra part number 18-2244 and is a JLM Marine OEM-equivalent product.

• Ensures a tight seal to prevent oil leaks and water contamination.
• Made from a durable rubber/composite material designed to withstand marine environments.
• Installation is straightforward, requiring only the replacement of the old seal during a gear oil change.

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.

Technical Specifications

Package Contents

• 1 x Gearcase Drain Plug Seal (Replaces 26-830749/8M0204693)
• This item is also sold in a 10-pack configuration.

Installation Guide

1. Position the boat on level ground and trim the engine or sterndrive to the vertical position.
2. Place an oil drain pan under the lower unit.
3. Locate and remove both the lower (drain) and upper (vent) gearcase screws using a large flathead screwdriver.
4. Allow the gear oil to drain completely. Note the color of the oil; a milky or creamy appearance indicates water contamination.
5. Remove the old seals from both screws and discard them.
6. Clean the threads of both screws and the seating surfaces on the gearcase.
7. Install a new seal onto each of the two gearcase screws.
8. Insert the gear lube pump or tube into the lower drain hole and fill until lubricant flows out of the upper vent hole.
9. Re-install the upper vent screw with its new seal first, then quickly remove the lube filler and re-install the lower drain screw with its new seal.
10. Tighten both screws securely, but do not overtighten. Clean any excess lubricant and check for leaks after a few minutes.

Troubleshooting & FAQ

Q: How do I know if this seal will fit my engine?
A: This seal is a direct replacement for Mercury part 26-830749 / 8M0204693 and fits a wide range of Mercury/Mariner outboards (30-300 HP) and MerCruiser Alpha/Bravo sterndrives. Please check the "Compatible Engine Models" table and verify your OEM part number to confirm fitment.

Q: How often should I replace the gearcase drain plug seals?
A: It is highly recommended to replace the drain plug seals every time you change your gearcase oil. Reusing old, compressed seals can lead to a poor fit, causing oil leaks or water intrusion.

Q: What are the signs of a failing drain plug seal?
A: Common signs include visible gear oil leakage around the drain screw or observing a milky, "coffee-colored" appearance in your gear lube when draining it. A milky color is a clear indicator of water contamination, which can cause severe damage to your gears if not addressed.

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.