Lower Unit Drain Plug Gasket – Fits Mercury, Mercruiser, Evinrude (Replaces 12-19183-3, 18-2244)

$7.99 $12.00

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Lower Unit Drain Plug Gasket – Fits Mercury, Mercruiser, Evinrude (Replaces 12-19183-3, 18-2244) is backordered and will ship as soon as it is back in stock.

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Product Details

This Lower Unit Drain Plug Gasket ensures a reliable seal for the gearcase drain and fill screws on a wide range of outboard and sterndrive models. It is directly compatible with Mercury and Mercruiser (25–400 HP, all years), as well as Evinrude, Johnson, and Tohatsu outboards that use a 3/8-16 drain/fill screw. It is not compatible with Japanese-origin Mercury/Mariner models.

This gasket serves as a direct cross-reference for Mercury parts 12-19183, 12-19183-3, and 12-19183Q02; Sierra 18-2244 and 18-2945; SEI 98-102-09; Mallory 9-60101; and GLM 31170, among other equivalents.

Installs on the 3/8-16 drain/fill screw, fitting between the screw head and the gearcase housing.
Constructed from a durable, blue, oil-resistant sealing material (plastic/nylon) for a long-lasting seal.
It is best practice to replace this gasket with every lower unit oil change to prevent leaks and water intrusion.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

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

Confirm your engine model/year in the table below.

Mercury/Mercruiser: Fits most outboards from 25 to 400 HP and all sterndrive models. Note the exclusion for models manufactured in Japan.

Evinrude/Johnson/Tohatsu: Broadly fits models using a 3/8-16 drain and fill screw.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercury	Outboards	25–400	2- & 4-Stroke	All	12-19183-3	Not for Japanese-origin models
Mercury	Mariner	25–400	2- & 4-Stroke	All	12-19183-3	Not for Japanese-origin models
Mercruiser	All Stern Drives			All	12-19183-3	For 3/8-16 drain/fill screws
Evinrude	Outboards	All	2- & 4-Stroke	All		For 3/8-16 drain/fill screws
Johnson	Outboards	All	2- & 4-Stroke	All		For 3/8-16 drain/fill screws
Tohatsu	Outboards					For 3/8-16 drain/fill screws

Technical Specs

Product Type: Lower Unit Drain Plug Gasket/Seal Washer
Installation: Fits between drain/fill screw and gearcase housing
Connection: For use with 3/8-16 drain/fill screws
Fitting Type: Washer/Gasket
Housing Material: Oil-resistant sealing material (plastic/nylon)
Housing Color: Blue
Dimensions: Inner Diameter: ~9mm (0.35 in)
Outer Diameter: ~14mm (0.55 in)
Thickness: ~1.5mm (0.06 in)
Weight: ~0.31 oz (8.8 g) per set
Other Technical Attributes: Not compatible with Japanese-origin Mercury/Mariner outboards

What’s in the Box

Packages available in different quantities:

10 x Lower Unit Drain Plug Seal Gasket (Replaces 12-19183-3)
12 x Lower Unit Drain Plug Seal Gasket (Replaces 12-19183-3)
15 x Lower Unit Drain Plug Seal Gasket (Replaces 12-19183-3)
20 x Lower Unit Drain Plug Seal Gasket (Replaces 12-19183-3)

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/vent screw to allow air to enter and oil to drain completely.
Inspect the magnetic tip of the drain screw for any unusual metal shavings.
Remove and discard the old drain plug gasket from the screw.
Thoroughly clean the screw, its threads, and the gasket seating surface on the gearcase.
Slide the new gasket onto the drain screw.
Once all oil 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.

Troubleshooting & FAQ

How often must I replace this drain screw gasket?

This gasket should be replaced every time you change your lower unit gear lube. Reusing old gaskets can lead to oil leaks and water intrusion, which may cause costly gearcase damage.

Will this gasket fit my engine?

These gaskets are designed for a wide range of Mercury, Mercruiser, Evinrude, Johnson, and Tohatsu models that use a 3/8-16 drain/fill screw. Please consult the compatibility tables above to verify fitment. It is critical to note they are not compatible with Japanese-manufactured Mercury/Mariner outboards.

What are the signs of a failing drain plug gasket?

A common sign of a failed seal is a milky or cloudy appearance in your drained gear lube, which indicates water has contaminated the oil. You may also notice gear lube actively leaking from around the drain screw.

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

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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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