Lower Unit Seal Kit – Fits Tohatsu/Mercury/Nissan 4-6 HP (Replaces 369-87321-0, 369873210)

$43.99 $70.00

Shipping calculated at checkout.

Lower Unit Seal Kit – Fits Tohatsu/Mercury/Nissan 4-6 HP (Replaces 369-87321-0, 369873210) 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 Seal Kit - Fits Tohatsu/Mercury/Nissan 4-6 HP Outboards (Replaces 369-87321-0/369873210) provides all necessary seals for a complete gearcase service. It is designed for Tohatsu/Nissan 2-stroke (M5B/NS5B) and 4-stroke (MFS4/MFS5/MFS6, NSF4/NSF5/NSF6) outboards from 2002–2014, and is also compatible with Mercury 4HP, 5HP, and 6HP 4-stroke outboard motors.

It serves as a direct interchange for Tohatsu part numbers 369-87321-0, 369873210, 369873210M, 369873212M and Mercury numbers 27-8M0155392, 95220A2, 27-8M0134073, 8M0082882, and 27-8M0188431.

Installation: Installs as a direct replacement for the original seals.
Materials: Includes non-asbestos paper gaskets, rubber o-rings, and durable synthetic seals.
Function: A complete kit for servicing the lower unit/gearcase.

Part Number Matrix

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

Brand	Part Number	Superseded By	Notes
Tohatsu/Nissan	369-87321-0 / 369873210 / 369873210M	369873212M	Original part has been superseded.
Mercury	27-8M0155392 / 95220A2 / 27-8M0134073 / 8M0082882 / 27-8M0188431		Cross-references to the Tohatsu kit.

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Tohatsu and Nissan models, this kit fits a range of 2-stroke and 4-stroke engines from 2002 to 2014. Verify your specific model and year.

For Mercury models, this kit fits select 4, 5, and 6 HP 4-stroke engines, which are often rebranded Tohatsu powerheads.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Tohatsu	M5B	5	2-Stroke	2003	369-87321-0
Nissan	NS5B	5	2-Stroke	2003	369-87321-0
Tohatsu	MFS4A2, MFS5A2, MFS6A2	4, 5, 6	4-Stroke	2002	369-87321-0
Nissan	NSF4A2, NSF5A2, NSF6A2	4, 5, 6	4-Stroke	2002	369-87321-0
Tohatsu	MFS4B, MFS5B, MFS6B	4, 5, 6	4-Stroke	2005–2010	369-87321-0
Nissan	NSF4B, NSF5B, NSF6B	4, 5, 6	4-Stroke	2005–2010	369-87321-0
Tohatsu	MFS4C, MFS5C, MFS6C	4, 5, 6	4-Stroke	2011–2014	369-87321-0
Nissan	NSF4C, NSF5C, NSF6C	4, 5, 6	4-Stroke	2011–2014	369-87321-0
Mercury	F4, F5, F6	4, 5, 6	4-Stroke		27-8M0155392, 95220A2	Rebranded Tohatsu engines

Technical Specs

Product Type: Lower Unit Seal Kit
Installation: Direct replacement
Fuel Type: Gasoline
Housing Material: Non-asbestos paper gaskets, rubber o-rings, synthetic seals
Warranty: 1 Year (aftermarket versions)
Kit Contents: Complete seal kit for gearcase/lower unit service

What’s in the Box

1 x Gasket (332-60006-0)
1 x Oil Seal (369-60111-0)
1 x O-Ring (345-65015-0)
1 x Pump Case Gasket - Upper (369-65018-0)
1 x Pump Guide Plate Gasket (369-65029-0)
1 x Oil Seal (369-60223-0)
1 x Pump Case Gasket - Lower (369-65020-0)
1 x O-Ring (369-66021-1)
1 x O-Ring (332-66032-0)

Installation Notes

Disconnect the spark plug wire and drain the gearcase oil into a suitable container.
Remove the bolts securing the lower unit to the outboard's midsection and carefully detach it.
Disassemble the water pump housing and impeller, noting the orientation of all parts.
Carefully remove all old seals, o-rings, and gaskets from the gearcase and water pump components. Avoid scratching any sealing surfaces.
Thoroughly clean all mating surfaces to ensure they are free of old gasket material and corrosion.
Install the new seals and gaskets from the kit. Lightly lubricate rubber o-rings and seal lips with marine grease before installation.
Reassemble the water pump and lower unit components in the reverse order of disassembly.
Reinstall the lower unit onto the outboard, tightening bolts to the manufacturer's specified torque.
Refill the gearcase with fresh, recommended lower unit oil to the correct level.

Troubleshooting & FAQ

How do I know if my lower unit seals are failing?

Common signs of failing lower unit seals include milky, water-contaminated gear oil (check the drain screw), visible oil leaks around the propeller shaft or driveshaft housing, or a burnt smell from the gear oil. Regular inspection of the gear lube is the best diagnostic method.

Will this kit fix a leak from my gearcase?

Yes, this kit is designed to resolve leaks by replacing all the common seals and gaskets in the lower unit. If a leak persists after proper installation, the issue may be a cracked housing or a damaged sealing surface, which requires further inspection.

What is the difference between this kit and the OEM version?

Our kit is an aftermarket equivalent designed to meet or exceed OEM specifications. It is made with comparable high-quality materials, such as durable synthetic rubber seals and non-asbestos gaskets, to ensure reliable performance and longevity.

Do I need special tools for installation?

Standard mechanic's tools are generally sufficient. However, a seal puller can make removing old seals easier and safer, and a torque wrench is essential for correctly tightening lower unit bolts during reassembly.

How often should lower unit seals be replaced?

There is no fixed replacement interval, but it is good practice to inspect for leaks annually when you change the gearcase oil. We recommend replacing the seals whenever the lower unit is serviced or if any signs of water intrusion or oil leakage are found.

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.