Lower Unit Drain Plug Seal Gasket – Fits Mercury/MerCruiser Outboard/Sterndrive (Replaces 12-19183-3, 12-19183Q02, 12-19183K02)

$7.99 $12.00

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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.

Worry-free returns

You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).

You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).

If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.

Delivery and Shipping

Free standard shipping on all orders under 1 KG

If you have any questions, feel free to email us at info@sierramarines.com, and we’ll get back to you within 20–36 hours.

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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