Lower Unit Seal Kit – Fits Yamaha 75-90 HP (Replaces 688-W0001-20-00, 688-W0001-C0-00)
Lower Unit Seal Kit – Fits Yamaha 75-90 HP (Replaces 688-W0001-20-00, 688-W0001-C0-00) is backordered and will ship as soon as it is back in stock.
Couldn't load pickup availability
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 Lower Unit Seal Kit – Fits Yamaha 75-90 HP is a comprehensive aftermarket solution for servicing the gearcase on Yamaha 75-90 HP outboard engines, including both 2-Stroke and 4-Stroke models manufactured between 1984 and 2001. It includes the essential components to restore watertight integrity and prevent gear oil leaks.
This kit serves as a direct replacement for Yamaha parts 688-W0001-20-00 and 688-W0001-C0-00, and is an interchange for GLM 87837, Sierra 18-8218, and SEI 95-421-11K.
- Installs in the lower unit gearcase.
- Designed for standard rotation units only.
- Includes a full set of necessary seals, O-rings, and gaskets for a complete repair.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Superseded By |
|---|---|---|
| Yamaha | 688-W0001-20-00 | 688-W0001-C0-00 |
| Yamaha | 688-W0001-C0-00 | |
| GLM | 87837 | |
| Sierra | 18-8218 | |
| SEI | 95-421-11K |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This kit is verified to fit the following Yamaha outboard models.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 75HP | 75 | 2-Stroke | 1984–2001 | 688-W0001-20-00 | Superseded by 688-W0001-C0-00 |
| Yamaha | 80HP | 80 | 2-Stroke | 1984–2001 | 688-W0001-20-00 | Superseded by 688-W0001-C0-00 |
| Yamaha | 85HP | 85 | 2-Stroke | 1984–2001 | 688-W0001-20-00 | Superseded by 688-W0001-C0-00 |
| Yamaha | 90HP | 90 | 2-Stroke | 1984–2001 | 688-W0001-20-00 | Superseded by 688-W0001-C0-00 |
| Yamaha | F75 | 75 | 4-Stroke | 1998–2001 | 688-W0001-20-00 | Superseded by 688-W0001-C0-00 |
| Yamaha | F80 | 80 | 4-Stroke | 1998–2001 | 688-W0001-20-00 | Superseded by 688-W0001-C0-00 |
| Yamaha | F90 | 90 | 4-Stroke | 1998–2001 | 688-W0001-20-00 | Superseded by 688-W0001-C0-00 |
Technical Specs
- Product Type
- Lower Unit Gearcase Seal Kit
- Installation
- Lower Unit / Gearbox
- Rotation
- For standard rotation units
- Product Length
- 36.0 in
- Product Width
- 24.0 in
- Product Height
- 2.0 in
What’s in the Box
- A complete set of required seals, O-rings, and gaskets for a standard lower unit service.
Installation Notes
- Disconnect the negative battery terminal and safely drain the gearcase oil into a suitable container.
- Remove the propeller assembly and unbolt the lower unit from the engine's midsection.
- Carefully disassemble the gearcase, laying out all parts in order and noting the location of each seal, gasket, and O-ring.
- Thoroughly clean all mating surfaces, bearing carriers, and seal bores, removing all traces of old sealant and debris.
- Lubricate new seals and O-rings with marine grease and press them into place using appropriate drivers to ensure they are seated evenly.
- Reassemble all components according to the manufacturer's service manual, applying sealant where specified.
- Torque all bolts to the specified values in the correct sequence.
- Refill the gearcase with fresh, high-quality marine gear lubricant before reinstalling the lower unit.
Troubleshooting & FAQ
How do I know if my lower unit seals are failing?
The most common signs of seal failure are milky, water-contaminated gear oil (which looks like coffee with cream), visible oil leaks around the propeller shaft or driveshaft housing, or a burnt smell from the gearcase. Finding metal shavings on the magnetic drain plug is also a critical indicator.
Will this kit fit a counter-rotation model?
No, this seal kit is specifically designed for standard rotation lower units. Using it on a counter-rotation (left-hand) model may result in improper sealing and premature failure.
What is the recommended replacement interval for gearcase seals?
Seals should be inspected for drying, cracking, or leaking at every service interval (typically 100 hours or once per year). It is recommended to perform a full reseal every 3-5 years or 500 hours of operation, especially for boats used in saltwater.
Why is my gearcase still leaking after installing the new kit?
A persistent leak could be due to several factors: an improperly seated seal, a scored or damaged driveshaft/propeller shaft surface, a crack in the gearcase housing, or using the incorrect type of sealant. Ensure all surfaces are clean, smooth, and undamaged before reassembly.
Is this an OEM or aftermarket part?
This listing is an aftermarket replacement (not OEM). It is built to OEM-level specifications with comparable materials. All parts are manufactured in an ISO 9002 facility and are batch-inspected for quality and consistency.
What are the shipping speeds and costs?
We ship worldwide quickly—typical transit time is 5–15 days. Standard shipping is free to most regions, with expedited options available at checkout for an additional cost where applicable.
What is the warranty and return policy?
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 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.
