Lower Unit Seal Kit – Fits Tohatsu/Mercury/Nissan 4-6 HP (Replaces 369-87321-0, 369873210)
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.
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Delivery and Shipping
Delivery and Shipping
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Lower Unit Seal Kit – Fits Tohatsu/Mercury/Nissan 4-6 HP (Replaces ...
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.
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| Brand | Part Number | Superseded By | Notes |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| Tohatsu/Nissan | 369-87321-0 / 369873210 / 369873210M | 369873212M | Original part has been superseded.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.
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