Magnetic Drain Plug – Fits Mercury & MerCruiser Outboards & SternDrives (Replaces 8M0058389, 67892A1)

Product Details

This magnetic drain plug is a replacement lower-unit gear-lube drain and fill screw for compatible Mercury and MerCruiser marine applications. It is designed for MerCruiser sterndrives that use a 3/8-16 threaded drain/fill screw, including Alpha One, Alpha One Gen II, MC-1, TR, TRS, I, R, and MR drives. It also fits a wide range of Mercury and Mariner outboards using the same 3/8-16 drain/fill thread; verify the original plug and application before ordering.

The plug is cross-referenced to Mercury/QuickSilver 8M0058389, Mercury 67892A1, 67892A06, 67892A05, and 14834A1, as well as aftermarket references Sierra 18-2375, Sierra 18-23751-9, GLM 21731, and Mallory 9-72651.

• Threaded replacement plug supplied with a sealing component.
• Magnetic tip collects ferrous particles suspended in the gear lubricant.
• Suitable for lower-unit gear-lube drain and fill openings when the original application uses a 3/8-16 UNC plug.
• Verify the part number, thread size, and drive or outboard application before installation.

Part Number Matrix

The references below are provided for identification and cross-reference purposes. Confirm the application and dimensions before purchase.

Engine & Model Compatibility

Compatibility depends on the use of a 3/8-16 UNC drain/fill screw. Always compare the existing plug, thread size, sealing arrangement, and application before installation.

MerCruiser sterndrives: The plug is intended for compatible lower-unit gear-lube drain and fill openings on the following drive families:

For Mercury and Mariner outboards, verify that the engine uses a 3/8-16 drain/fill screw. The original listing identifies the Verado series as excluded; confirm the specific engine model before ordering.

Technical Specs

Product Type

Magnetic lower-unit gear-lube drain plug

Installation

Threaded plug with sealing component

Thread Size

3/8-16 UNC

Fitting Type

Threaded drain/fill plug

Material

Metal housing with magnetic element

Color

Chrome/silver

Function

Captures ferrous particles in the gear lubricant during service

What’s in the Box

• 1 x Magnetic lower-unit gear-lube drain/fill plug with sealing component

Installation Notes

1. Turn the engine off, place the drive unit in a suitable service position, and position a drain pan beneath the lower unit.
2. Use a large, correctly fitting flat-blade screwdriver to remove the lower drain plug and upper vent plug.
3. Allow the gear lubricant to drain completely. Inspect it for water contamination, a milky appearance, or unusual metal debris.
4. Clean the sealing surfaces around the drain and vent openings.
5. Install the magnetic plug in the lower opening with the sealing component in place. Tighten according to the manufacturer’s service guidance; do not overtighten.
6. Pump the manufacturer-recommended gear lubricant into the lower opening until it reaches the upper vent opening.
7. Install and tighten the upper vent plug.
8. Remove the lubricant-pump nozzle and promptly install and tighten the lower drain plug.
9. Wipe the drive clean and inspect both plugs for leaks after servicing.

Troubleshooting & FAQ

Safety & Important Information

• Service the gear case only with the engine stopped and the boat securely supported.
• Use the lubricant specified by the engine or drive manufacturer.
• Do not force the plug or overtighten it, as damaged threads or sealing surfaces can cause leaks.
• Verify the original part, thread size, and application before purchase and installation.
• Professional installation is recommended when the gear case, threads, or sealing surfaces are damaged.

About Sea Sierra

• Pro-Grade Standards — We supply marine replacement parts selected for demanding service environments.
• Global Fulfillment — Delivery options and estimated transit times are shown at checkout based on destination.
• Value-Focused Marine Parts — We aim to provide practical replacement solutions with clear application information.