Water Pump Service Kit with Housing for Yamaha 2-Stroke C25/C30 (1990–1997) – Replaces 689-W0078-A6, Sierra 18-3427
Water Pump Service Kit with Housing for Yamaha 2-Stroke C25/C30 (1990–1997) – Replaces 689-W0078-A6, Sierra 18-3427 is backordered and will ship as soon as it is back in stock.
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Water Pump Service Kit with Housing for Yamaha 2-Stroke C25/C30 (19...
Water Pump Service Kit with Housing for Yamaha 2-Stroke C25/C30 (1990–1997) – Replaces 689-W0078-A6, Sierra 18-3427 is backordered and will ship as soon as it is back in stock.
Product Details
This water pump service kit with housing is an aftermarket replacement for selected Yamaha 2-stroke outboards. It is specified for Yamaha C25 models from 1990 through 1997 and Yamaha C30 models from 1990.
The kit is identified by Yamaha reference 689-W0078-A6 and aftermarket reference Sierra 18-3427. It is intended to help restore the water pump assembly and maintain proper cooling-water circulation when the original service components are worn.
- Water pump service kit supplied with pump housing.
- Designed for selected Yamaha C25 and C30 2-stroke outboards.
- Use the exact engine model and year to confirm compatibility before ordering.
Part Number References
These references identify the product and its documented aftermarket replacement relationship.
| Reference Type | Part Number |
|---|---|
| Yamaha reference | 689-W0078-A6 |
| Aftermarket reference | 18-3427 |
Engine & Model Compatibility
Compatibility is limited to the Yamaha applications listed below. Confirm the model designation and production year from the engine identification label or service documentation before installation.
| Brand | Model | Rated HP | Stroke | Years | Reference | Notes |
|---|---|---|---|---|---|---|
| Yamaha | C25 | 25 HP | 2-Stroke | 1990–1997 | 689-W0078-A6 | Selected C25 applications; verify the complete model designation. |
| Yamaha | C30 | 30 HP | 2-Stroke | 1990 | 689-W0078-A6 | 1990 application only as documented. |
Important: This listing does not confirm fitment for every Yamaha 25–30 HP outboard or for Mercury/Mariner models. Do not rely on horsepower alone; model and year must match the documented applications.
Technical Specifications
- Product Type
- Water pump service kit with housing
- Application
- Selected Yamaha 2-stroke C25 and C30 outboards
- Service Function
- Water pump assembly service and cooling-water circulation maintenance
- Replacement Reference
- Yamaha 689-W0078-A6; aftermarket 18-3427
- Product Status
- Aftermarket replacement, not a Yamaha-branded OEM component
What’s in the Box
This product is supplied as a water pump service kit with housing. The company specification does not provide a verified item-by-item component list or quantities, so individual seals, gaskets, fasteners, impeller details, and other small parts should not be assumed beyond the stated kit configuration.
Installation Notes
- Confirm that the engine is a documented Yamaha C25 or C30 2-stroke application and that the model year matches the compatibility information above.
- Disconnect the battery where applicable, place the outboard in neutral, and follow the engine manufacturer’s service procedures.
- Remove the lower unit according to the service manual, taking care not to damage the shift linkage, driveshaft, or water tube.
- Remove the existing water pump housing and service components. Record component orientation before disassembly.
- Clean the mating surfaces and inspect the driveshaft, keyway, water tube, and surrounding components for wear or corrosion.
- Install the replacement service kit with housing using the correct installation orientation and any required sealing materials specified by the engine service manual.
- Tighten fasteners to the manufacturer’s specified torque values and reinstall the lower unit.
- Test the outboard in a suitable water supply and confirm a steady cooling-water tell-tale stream before normal operation.
Professional installation is recommended if you are not familiar with outboard lower-unit or water-pump service.
Troubleshooting & FAQ
How do I confirm that this service kit fits my engine?
Verify the engine brand, C25 or C30 model designation, 2-stroke configuration, and model year. The documented range is Yamaha C25 from 1990–1997 and Yamaha C30 from 1990. Horsepower alone is not sufficient for fitment confirmation.
What symptoms may indicate a worn water pump?
Possible symptoms include overheating, reduced cooling-water flow, or a weak or missing tell-tale stream. Stop operation if the engine overheats and diagnose the cooling system before continuing to run it.
Does this listing fit all Yamaha 25 HP and 30 HP outboards?
No. The documented applications are limited to selected Yamaha C25 and C30 2-stroke models and years shown in the compatibility table. Check the complete model designation before ordering.
Is this an OEM Yamaha part?
No. This is an aftermarket replacement identified to replace the Yamaha reference 689-W0078-A6. Yamaha is a trademark of its respective owner and is used only to identify compatibility.
Does this listing fit Mercury or Mariner outboards?
Mercury and Mariner applications are not included in the company’s documented fitment for this exact product. Do not purchase for those engines based only on a similar part-number listing.
How often should a water pump be serviced?
Service intervals vary by engine, operating conditions, and the manufacturer’s recommendations. Follow the maintenance schedule in your engine service manual and inspect the cooling system whenever cooling-water flow becomes weak or irregular.
Safety & Important Information
- Verify the complete engine model and year before purchase.
- Do not operate an outboard that is overheating or has inadequate cooling-water flow.
- Use the manufacturer’s service manual for disassembly procedures, torque specifications, sealing requirements, and final testing.
- Product references identify compatibility and replacement relationships; they do not indicate that this aftermarket product is manufactured by Yamaha or Sierra.
About Sea Sierra
- Marine Replacement Parts — Parts selected for documented marine applications and service requirements.
- Application-Focused Listings — Compatibility information is presented by engine model, stroke, horsepower, and year where documented.
- Support for Maintenance — Clear product references help customers identify replacement parts for routine outboard service.
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