Water Pump Repair Kit for Yamaha 20/25 HP 2-Stroke 2-Cylinder Outboards — Without Housing
Water Pump Repair Kit for Yamaha 20/25 HP 2-Stroke 2-Cylinder Outboards — Without Housing is backordered and will ship as soon as it is back in stock.
Worry-free returns
Worry-free returns
Shop with confidence. If you’re not completely satisfied, eligible items may be returned within the return window, provided they are unused and in original packaging.
If the return is due to our error or a defective item, we’ll make it right.
Please contact us before returning any item.
Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
U.S. orders usually arrive within 6–15 days, depending on stock location and destination.
International delivery times may vary due to customs processing.
Tracking information will be provided once your order ships.
Water Pump Repair Kit for Yamaha 20/25 HP 2-Stroke 2-Cylinder Outbo...
Water Pump Repair Kit for Yamaha 20/25 HP 2-Stroke 2-Cylinder Outboards — Without Housing is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket Water Pump Repair Kit is designed to service the water pump on selected Yamaha 20 and 25 HP, two-cylinder, 2-stroke outboard engines. The kit is supplied without the water pump housing and is intended for rebuilding an existing housing with worn internal service components.
The kit corresponds to Yamaha OEM reference 6L2-W0078-00-00 and Sierra Marine aftermarket reference 18-3431. These references are provided for identification and cross-reference purposes; always compare the part number and application with your engine documentation before ordering.
- For selected Yamaha 20 and 25 HP two-cylinder 2-stroke outboards.
- Service-kit configuration without the water pump housing.
- Helps restore water-pump sealing and cooling-water circulation when installed correctly.
- Use with the existing housing only if it is serviceable and within the manufacturer's dimensional limits.
Part Number References
| Brand | Part Number | Reference Type |
|---|---|---|
| Yamaha | 6L2-W0078-00-00 | OEM reference |
| Sierra Marine | 18-3431 | Aftermarket cross-reference |
Engine Compatibility
Company application data identifies this repair kit for Yamaha 20 and 25 HP, 2-cylinder, 2-stroke outboard engines. Catalog records associate the OEM reference with multiple Yamaha model and year applications, including examples from the late 1980s through the 2000s. Because fitment can vary by model code, production year, shaft configuration, and serial range, confirm the complete engine identification and compare the existing water-pump components before installation.
| Brand | Horsepower | Cylinders | Stroke | Application | Housing |
|---|---|---|---|---|---|
| Yamaha | 20–25 HP | 2-cylinder | 2-Stroke | Selected Yamaha outboard models; verify model, year, and serial range | Not included |
Technical Specifications
- Product Type
- Water pump repair kit
- Application
- Outboard engine cooling system
- Engine Brand
- Yamaha Outboard
- Horsepower Range
- 20–25 HP
- Engine Configuration
- 2-cylinder, 2-stroke
- Housing
- Not included; reuse the existing serviceable housing
- Product Status
- Aftermarket replacement
What’s in the Box
The kit is supplied as a water-pump service kit without the housing. The service components associated with this application include:
- Water pump impeller
- Insert cup or cartridge insert
- Wear plate or outer plate
- Water-pump gaskets and sealing components as supplied for the kit configuration
- Replacement mounting bolts or fasteners as supplied for the kit configuration
Important: Exact component quantities and included small hardware may vary by production batch. The water pump housing is not included. Do not assume that a driveshaft key or separate O-ring is included unless it is shown in the supplied package or confirmed by the seller.
Installation Notes
- Confirm the engine model, year, serial range, and existing water-pump reference before disassembly.
- Disconnect the battery where applicable, place the engine securely, and follow the manufacturer's service-manual safety procedures.
- Remove the lower unit and water-pump assembly according to the engine service manual.
- Inspect the existing housing, driveshaft, keyway, plates, cup, and fasteners for corrosion, scoring, distortion, or excessive wear.
- Clean all mating surfaces carefully and remove old gasket material without damaging the sealing surfaces.
- Install the supplied service components in the correct order and orientation. Lubricate and orient the impeller vanes according to the manufacturer's instructions.
- Reuse the existing housing only when it is in suitable condition. Replace any damaged component that is not included in this kit.
- Reassemble the water pump and lower unit, tightening fasteners to the manufacturer's specified torque.
- After installation, run the engine in an appropriate test environment and confirm a strong, steady cooling-water tell-tale stream before normal use.
Troubleshooting & FAQ
Does this kit include the water pump housing?
No. This product is the without-housing configuration. It is intended to service an existing compatible water-pump housing.
Which engines is this kit for?
The company application is Yamaha 20 and 25 HP, 2-cylinder, 2-stroke outboard engines. Exact fitment depends on the engine model, year, shaft configuration, and serial range, so compare the complete engine identification with the service manual before ordering.
What part numbers does this kit replace or cross-reference?
The primary references are Yamaha 6L2-W0078-00-00 and Sierra Marine 18-3431. Cross-reference numbers should be used together with the confirmed engine application, not as a substitute for checking model and serial conditions.
Is this an OEM Yamaha kit?
No. This listing is for an aftermarket replacement kit. Yamaha part numbers are shown only as application and identification references.
How can I tell if the water pump needs service?
Common signs include a weak or intermittent tell-tale stream, overheating, reduced cooling-water flow, or visible wear and cracking on the impeller and related pump components. Diagnose the complete cooling system before replacing parts.
Can I install this kit without professional help?
Water-pump service requires removal of the lower unit and correct reassembly. Use the engine manufacturer's service manual and seek qualified marine-technician assistance if you are not experienced with outboard maintenance.
Safety & Important Information
- Verify the complete engine model, year, serial range, and part-number application before purchase.
- Confirm that the existing water-pump housing is compatible and serviceable; the housing is not included.
- Do not operate an outboard with inadequate cooling-water flow.
- Follow the manufacturer's service procedures, torque specifications, and testing requirements.
- This is an aftermarket replacement product and is not manufactured by Yamaha or Sierra Marine.
About Sea Sierra
- Marine replacement parts selected for practical service and repair applications.
- Clear cross-reference information to help customers identify the correct application.
- Support focused on accurate fitment and responsible installation.
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.
