Yamaha Gear Housing Seal Kit – Fits Yamaha 20C/25/C25/30/C30 Outboards (Replaces 689-W0001-C2)
Yamaha Gear Housing Seal Kit – Fits Yamaha 20C/25/C25/30/C30 Outboards (Replaces 689-W0001-C2) 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 Yamaha Gear Housing Seal Kit is designed to service the lower units on a range of Yamaha 20-30 HP 2-Stroke outboards, specifically models 20C, 25, C25, 30, and C30 from 1984–1997. It provides the essential seals to prevent water intrusion and lubricant leaks in the gearcase.
This kit serves as a direct replacement for Yamaha part number 689-W0001-C2-00 and Sierra 18-0023, offering an exact-fit solution for lower unit maintenance.
- Engineered as a direct replacement part for straightforward installation.
- Constructed from high-quality rubber, metal, and plastic components to resist wear and corrosion.
- Includes all necessary seals and O-rings for a complete gear housing service.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 689-W0001-C2-00 |
| Sierra | 18-0023 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This seal kit is designed for select Yamaha 2-stroke outboards from the 1980s and 1990s. Please verify your specific model and year.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | C30 | 30 | 2-Stroke | 1990–1991 | 689-W0001-C2 | |
| Yamaha | C20 | 20 | 2-Stroke | 6A9 | 689-W0001-C2 | |
| Yamaha | 30 | 30 | 2-Stroke | 1986 | 689-W0001-C2 | |
| Yamaha | C25 | 25 | 2-Stroke | 1990–1991 | 689-W0001-C2 | |
| Yamaha | 25 | 25 | 2-Stroke | 1986–1987 | 689-W0001-C2 | (2-cyl) |
| Yamaha | CV25 | 25 | 2-Stroke | 1990 | 689-W0001-C2 |
Technical Specs
- Product Type
- Gear Housing/Lower Unit Seal Kit
- Installation
- Direct replacement for original equipment
- Materials
- Machined from high-quality aluminum, steel, and rubber for maximum hardness, wear resistance, and corrosion resistance
- Dimensions
- 6.0 in x 7.5 in x 0.5 in
- Weight
- 0.05 lbs (0.023 kg)
What’s in the Box
- All necessary replacement seals and o-rings required for gear housing service.
Installation Notes
- Drain the gearcase lubricant completely into an approved container.
- Remove the propeller and then unbolt and detach the lower unit from the outboard's midsection.
- Disassemble the gearcase components as required to access the propeller shaft and driveshaft seals.
- Carefully extract all old seals and O-rings, taking care not to scratch the housing surfaces.
- Thoroughly clean all sealing surfaces of residue and old sealant.
- Lightly coat the new seals with marine grease before carefully pressing them into place.
- Reassemble the gearcase, ensuring all components are correctly seated and torqued to spec.
- Refill the gearcase with the manufacturer-recommended lubricant to the proper level.
- Once reinstalled, check for any signs of leaks before operating the engine on the water.
Troubleshooting & FAQ
How do I know if this seal kit will fit my Yamaha outboard?
This kit is specifically designed for Yamaha 20-30HP 2-Stroke models manufactured between 1984–1997, including the 20C, 25, C25, 30, and C30 series. Always cross-reference your OEM part number (689-W0001-C2) and check our compatibility table to ensure a perfect match.
What are the signs that my gear housing seals are failing?
The most common indicators of a bad seal are water intrusion into the gear lube (making it milky or creamy), visible oil leaks from the propeller shaft area, or an unusual burning smell from the lower unit after operation.
How often should I replace my lower unit seals?
It is recommended to inspect gear lube at every service interval. Seals should be replaced as a preventative measure every 1-2 seasons or 100-200 hours of use, or immediately if you notice any signs of leaks or water contamination.
Is this a complete kit for the entire lower unit?
This kit contains the primary seals for the gear housing assembly (lower unit). While it covers the most common replacement needs for the specified models, always consult your engine's service manual to confirm it includes every single seal required for your specific service job.
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
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