Propeller Shaft Oil Seal – Fits Mercury/Mariner 30-125 HP (Replaces 26-70081)

$15.99 $25.00

Shipping calculated at checkout.

Propeller Shaft Oil Seal – Fits Mercury/Mariner 30-125 HP (Replaces 26-70081) 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 aftermarket Propeller Shaft Oil Seal is designed for a wide range of Mercury and Mariner outboard lower units, covering models from 30 HP to 125 HP manufactured between 1978 and the present. It serves as a crucial component in the gearcase to prevent water from entering and to retain gear oil, ensuring the longevity and performance of your engine's drivetrain.

It is a direct replacement for Mercury part 26-70081 and interchanges with other aftermarket numbers including Sierra 18-2053, GLM 85530, Quicksilver 26-70081, and UAN Marine 91255-zw1-003.

Installs via press fit into the lower unit gearcase.
Constructed from durable Nitrile Rubber (NBR) for a reliable seal.
Prevents water intrusion and retains essential gear oil.

Part Number Matrix

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

Brand	Part Number
Mercury	26-70081
Sierra	18-2053
GLM	85530
Quicksilver	26-70081
UAN Marine	91255-zw1-003

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Mercury and Mariner models, this seal fits a broad variety of 2-stroke and 4-stroke engines from 30 to 125 HP. Verify your specific model and year range for an exact match.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.
Mercury	30 HP	30	2-Stroke	1979–1997	26-70081
Mercury	35 HP	35	2-Stroke	1984–1989	26-70081
Mercury	40 HP	40	2-Stroke	1978–1997	26-70081
Mercury	45 HP	45	2-Stroke	1986–1989	26-70081
Mercury	50 HP	50	2-Stroke	1978–1997	26-70081
Mercury	60 HP	60	2-Stroke	1979–1991	26-70081
Mercury	65 HP	65	3-cyl	1979–1985	26-70081
Mercury	70 HP	70	3-cyl	1979–1985	26-70081
Mercury	75 HP	75	3-cyl	1978–1997	26-70081
Mercury	80 HP	80	3-cyl	1978–1989	26-70081
Mercury	90 HP	90	3-cyl	1978–1997	26-70081
Mercury	100 HP	100	4-cyl	1978–1990	26-70081
Mercury	115 HP	115	4-cyl	1978–1997	26-70081
Mercury	125 HP	125	4-cyl	1978–1997	26-70081
Force	75-120 HP	75-120	2-Stroke	1989-1999	26-70081

Also compatible with select Force by Mercury Marine outboards from the late 1990s.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.
Force	75	75	2-Stroke	1999	26-70081
Force	90	90	2-Stroke	1995–1999	26-70081
Force	120	120	2-Stroke	1995–1999	26-70081

Technical Specs

Product Type: Propeller Shaft Oil Seal
Installation: Lower Unit / Gearcase
Connection: Press Fit
Housing Material: Nitrile Rubber (NBR)
Housing Color: Black
Dimensions: Inner Diameter: 30.2 mm (1.188 in), Outer Diameter: 43 mm (1.689 in), Width: 6.3 mm (0.247 in)
Fitting Type: Press Fit
Other Technical Attributes: Prevents water intrusion and retains gear oil in lower unit

What’s in the Box

1 x Propeller Shaft Oil Seal (26-70081)

Installation Notes

Position the lower unit securely on a workbench. Place a drain pan underneath the gearcase.
Remove the lower drain screw to empty the gear oil completely. Inspect the oil for any milky appearance, indicating water intrusion.
Remove the propeller assembly, including the propeller nut, thrust washer, and any spacers.
Carefully pry out the old propeller shaft oil seal using a seal puller or a flat screwdriver. Be cautious not to scratch or gouge the housing.
Thoroughly clean the seal housing area to remove any old sealant, corrosion, or debris.
Apply a thin layer of marine grease or a suitable sealant to the outer edge of the new oil seal.
Gently press the new seal into place using a socket or seal driver that matches the outer diameter of the seal. Ensure it is seated evenly and fully.
Lubricate the propeller shaft and the inner lip of the new seal with marine grease.
Reinstall the propeller assembly, ensuring all spacers and washers are in the correct order. Torque the propeller nut to the manufacturer's specification.
Refill the lower unit with the recommended gear oil through the bottom drain hole until it seeps out of the upper vent hole, then replace and tighten both screws.

Troubleshooting & FAQ

How do I know if this oil seal will fit my specific engine model?

This seal is designed for a wide range of Mercury/Mariner (30-125 HP) and Force (75-120 HP) outboards. The best way to confirm is to check the compatibility tables on this page against your engine's model, horsepower, and year. Cross-referencing your old part number with the ones listed in our Part Number Matrix is also a reliable method.

What are the signs of a failing propeller shaft oil seal?

The most common sign is a milky or creamy appearance in your gear lube, which indicates water has mixed with the oil. You may also notice an oil leak around the propeller shaft area or find fishing line tangled behind the propeller, which can damage the seal and cause it to fail.

How often should I replace my lower unit seals?

There is no fixed replacement interval, but it's good practice to inspect your gear lube annually. It's recommended to replace the seals whenever you perform major service on the lower unit, if you notice any signs of a leak, or if the boat is used heavily in saltwater or commercial applications.

Can I reuse this seal if I remove the propeller shaft for other maintenance?

No. Oil seals are designed for a single installation. Once removed, they can become stretched or damaged, and will not provide a reliable seal if reinstalled. Always use a new seal during reassembly to prevent leaks.

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.

Payment & Security

Payment methods

Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.