Lower Unit Seal Kit – Fits Yamaha 75-90 HP (Replaces 688-W0001-22-00, 688-W0001-21-00)
Lower Unit Seal Kit – Fits Yamaha 75-90 HP (Replaces 688-W0001-22-00, 688-W0001-21-00) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Product Details
This is a complete Lower Unit Seal Kit for Yamaha 75-90 HP, 2-Stroke outboard motors manufactured between 1989 and 2006. It fits a wide range of models, including the C75, E75, P75, C80, C85, CV85E, 90, B90, and C90 series engines.
This kit serves as a direct replacement for Yamaha OEM part numbers 688-W0001-22-00 and 688-W0001-21-00, and is interchangeable with Sierra 18-0021 and WSM 9-74502.
- Contains all necessary seals, gaskets, and O-rings for a complete lower unit service.
- Designed for durability to prevent water intrusion and oil leaks.
- Professional installation is recommended for optimal performance and safety.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 688-W0001-22-00 |
| Yamaha | 688-W0001-21-00 |
| Sierra | 18-0021 |
| WSM | 9-74502 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | C75 | 75 | 2-Stroke | 1994–1999 | 688-W0001-22-00 | |
| Yamaha | P75 | 75 | 2-Stroke | 1996–1999 | 688-W0001-22-00 | |
| Yamaha | E75 | 75 | 2-Stroke | 1995–2000 | 688-W0001-22-00 | |
| Yamaha | C80 | 80 | 2-Stroke | 1997 | 688-W0001-22-00 | |
| Yamaha | C85 | 85 | 2-Stroke | 1992–1996 | 688-W0001-22-00 | |
| Yamaha | CV85E | 85 | 2-Stroke | 1989–1991 | 688-W0001-22-00 | |
| Yamaha | 90 | 90 | 2-Stroke | 1992–2006 | 688-W0001-22-00 | |
| Yamaha | B90 | 90 | 2-Stroke | 1998–1999 | 688-W0001-22-00 | |
| Yamaha | C90 | 90 | 2-Stroke | 1997–2001 | 688-W0001-22-00 |
Technical Specs
- Product Type
- Lower Unit Gearcase Seal Kit
- Dimensions
- 13.0" L x 10.0" W x 0.5" H
- Installation
- Professional installation recommended
- Warranty
- 1 year (Peach Motor Parts)
- Kit Contents
- Contains complete seals for lower unit service
What’s in the Box
- Complete lower unit gearcase seal kit
- Includes all necessary seals, gaskets, and O-rings for a full lower unit service.
Installation Notes
- Disconnect the battery and safely drain the gearcase oil into a suitable container.
- Unbolt and carefully lower the gearcase assembly from the outboard's midsection.
- Systematically disassemble the lower unit, keeping all components organized. Pay close attention to the order and orientation of shims and bearings.
- Remove all old seals, gaskets, and O-rings. Thoroughly clean all sealing surfaces to ensure they are free of debris and corrosion.
- Install the new seals and O-rings from the kit, using appropriate seal drivers to ensure they are seated correctly and not damaged.
- Reassemble the gearcase, torquing all fasteners to the manufacturer's specified values.
- Before reinstalling on the engine, perform both a vacuum and pressure test on the gearcase to confirm a proper seal.
- Refill the gearcase with the correct type and amount of new marine gear lubricant.
Troubleshooting & FAQ
How do I know if this seal kit fits my specific Yamaha engine?
This kit is designed for Yamaha 75-90 HP 2-stroke outboard models from approximately 1989 to 2006. The most reliable way to confirm fitment is to check your engine model and year against the detailed "Engine & Model Compatibility" table provided on this page.
What are the signs of a failing lower unit seal?
The most common sign is "milky" or water-contaminated gear oil, which you can see when draining the lubricant. Other indicators include visible oil leaks around the propeller shaft or driveshaft housing, or a metallic sheen in the drained oil, which suggests water intrusion is causing internal gear wear.
Do I need special tools for installation?
Yes, installation requires specialized tools such as a bearing puller, a seal driver set, and a torque wrench. Because of the precision and tools needed to ensure a lasting repair, we strongly recommend professional installation by a qualified marine mechanic.
How often should lower unit seals be replaced?
As a best practice, lower unit seals should be inspected for leaks annually during routine service. We recommend replacing them proactively every 2-3 years or after 200-300 hours of use, especially if the boat is operated primarily in saltwater.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). It has been built to meet or exceed OEM-level specifications using comparable materials. Our parts are manufactured in an ISO 9002 certified facility and are batch-inspected to ensure consistent quality and performance.
Shipping speed & cost
We ship worldwide quickly—typical transit time is 5–15 days. Standard shipping is free to most locations; any available expedited options and their costs will be displayed at checkout.
Warranty & returns
This product is covered by a 1-year warranty against manufacturing defects under normal use. If you encounter any issues, please contact our support team with your order details. Returns are accepted within our standard window for items that are unused and in their 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 quality control.
Payment & Security
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