Water Pump Repair Kit Without Housing for Yamaha 25/30 HP 2-Stroke Outboards – Replaces 6J8-W0078-A2-00 and 6J8-W0078-A1-00
Water Pump Repair Kit Without Housing for Yamaha 25/30 HP 2-Stroke Outboards – Replaces 6J8-W0078-A2-00 and 6J8-W0078-A1-00 is backordered and will ship as soon as it is back in stock.
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Water Pump Repair Kit Without Housing for Yamaha 25/30 HP 2-Stroke ...
Water Pump Repair Kit Without Housing for Yamaha 25/30 HP 2-Stroke Outboards – Replaces 6J8-W0078-A2-00 and 6J8-W0078-A1-00 is backordered and will ship as soon as it is back in stock.
Product Details
This water pump repair kit without housing is designed for selected Yamaha 25 HP and 30 HP 2-stroke outboard motors. It provides the service components needed to renew the water pump assembly and help restore proper cooling-water flow. The kit is intended for lower-unit installation and does not include the water pump housing.
The company fitment information covers 25 HP and 30 HP 2-stroke, 3-cylinder applications from 1996–2002, plus 30 HP 2-stroke applications from 1982–1995. Always confirm the complete engine model and the part number removed from your outboard before ordering.
- Installation location: Lower unit / gearcase water pump assembly.
- Product type: Water pump service and repair kit.
- Housing: Not included.
- Aftermarket reference: Sierra 18-3430.
Part Number Matrix
These are the manufacturer and aftermarket references associated with this water pump repair kit. Part-number references are provided for identification and should be checked against the exact engine application.
| Brand | Part Number | Reference Type |
|---|---|---|
| Yamaha | 6J8-W0078-A2-00 | OEM reference |
| Yamaha | 6J8-W0078-A1-00 | OEM reference |
| Sierra | 18-3430 | Aftermarket reference |
Engine & Model Compatibility
The company catalog identifies the following fitment scope. Engine model codes, production variations, and serial-number conditions can affect compatibility, so use the part number and complete engine identification together.
| Brand | Rated HP | Stroke | Cylinder Configuration | Year Range | OEM Reference | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 25 | 2-Stroke | 3-Cylinder | 1996–2002 | 6J8-W0078-A2-00 | Confirm the complete engine model. |
| Yamaha | 30 | 2-Stroke | 3-Cylinder | 1996–2002 | 6J8-W0078-A2-00 | Confirm the complete engine model. |
| Yamaha | 30 | 2-Stroke | Not specified in company fitment record | 1982–1995 | 6J8-W0078-A1-00 | Confirm the complete engine model and original part. |
Technical Specs
- Product Type
- Water Pump Repair Kit
- Application
- Yamaha 25 HP and 30 HP 2-stroke outboard water pump service
- Installation
- Lower unit / gearcase
- Housing Included
- No
- Fitment Scope
- 25/30 HP 2-stroke applications from 1996–2002 and 30 HP 2-stroke applications from 1982–1995, subject to exact model confirmation
- Reference Numbers
- Yamaha 6J8-W0078-A2-00; Yamaha 6J8-W0078-A1-00; Sierra 18-3430
What’s in the Box
This is a water pump service kit supplied without the water pump housing. The component list below describes the supplied repair components:
- 1 x Cartridge insert (663-44322-00-00)
- 1 x Impeller (6H4-44352-02-00)
- 1 x Water pump gasket (663-44315-A0-00)
- 1 x Outer plate, cartridge (663-44323-00-00)
- 1 x Cartridge gasket (663-44324-A0-00)
- 1 x Water pump gasket (663-44316-A0-00)
- 2 x Bolt with washer (90119-08M13-00)
- 2 x Bolt with washer (90119-08M34-00)
- Water pump housing: not included
Installation Notes
- Disconnect the battery and place the outboard in neutral.
- Remove the lower unit from the outboard and place it securely on a stable workbench.
- Remove the water pump cover or housing and note the order and orientation of the existing components.
- Remove the old impeller, gaskets, plates, cartridge components, and related hardware that are being replaced.
- Clean all mating surfaces carefully and remove old gasket material, debris, and corrosion.
- Install the supplied components in the correct order for the engine model. Confirm that the housing is serviceable before reassembly because a replacement housing is not supplied.
- Install the impeller with the vanes oriented correctly. Follow the engine manufacturer’s service procedure for driveshaft rotation and impeller installation.
- Reinstall the water pump cover or housing and tighten fasteners to the manufacturer’s specified torque.
- Reattach the lower unit, aligning the driveshaft, shift shaft, and water tube.
- Test the outboard using an appropriate water source and verify steady cooling-water flow before normal operation.
Troubleshooting & FAQ
How do I confirm fitment?
Check the outboard brand, horsepower, stroke, cylinder configuration, year, complete model designation, and the part number from the existing water pump kit. The catalog scope covers Yamaha 25 HP and 30 HP 2-stroke applications from 1996–2002, along with Yamaha 30 HP 2-stroke applications from 1982–1995.
Does this kit include the water pump housing?
No. This is a water pump repair kit supplied without the housing. Inspect the existing housing for wear, grooves, cracks, or other damage before installation.
What symptoms can indicate a worn water pump?
A weak or intermittent tell-tale stream, overheating, reduced cooling-water flow, or a brittle, cracked, or damaged impeller can indicate that the water pump requires service. Diagnose the complete cooling system before replacing parts.
Is the Sierra number an OEM part number?
No. Sierra 18-3430 is an aftermarket reference. Yamaha 6J8-W0078-A2-00 and 6J8-W0078-A1-00 are the manufacturer references associated with the listed applications.
Can I use this kit on any Yamaha 25 HP or 30 HP outboard?
No. Horsepower alone does not establish fitment. Confirm the complete model, year, stroke, cylinder configuration, and existing water pump part number before ordering.
How often should the impeller be inspected?
Inspect the impeller according to the engine manufacturer’s maintenance schedule and whenever cooling-water flow is reduced. More frequent inspection may be appropriate when operating in saltwater, muddy water, or sandy conditions.
Safety & Important Information
- Disconnect the battery and follow the outboard manufacturer’s service instructions before beginning work.
- Verify the exact engine model and part number before ordering; a horsepower match alone is not sufficient.
- The water pump housing is not included. Reuse it only if inspection confirms that it is serviceable.
- Use the manufacturer’s torque values and installation procedure for your specific engine.
- Test the cooling-water system before operating the outboard under load.
- This is an aftermarket replacement kit and is not an original Yamaha component.
About Sea Sierra
- Marine Replacement Parts — We supply replacement components for common outboard maintenance and repair applications.
- Application-Focused Information — Product details are organized around engine specifications and manufacturer references to help support accurate part selection.
- Service-Oriented Support — Confirm the complete engine identification and existing part number whenever fitment depends on model or year variations.
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