Water Pump Repair Kit – Fits Yamaha 25/30 HP 2-Stroke (Replaces 6J8-W0078-A2-00, 879136)
Water Pump Repair Kit – Fits Yamaha 25/30 HP 2-Stroke (Replaces 6J8-W0078-A2-00, 879136) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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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.
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Water Pump Repair Kit – Fits Yamaha 25/30 HP 2-Stroke (Replaces 6J8...
Water Pump Repair Kit – Fits Yamaha 25/30 HP 2-Stroke (Replaces 6J8-W0078-A2-00, 879136) is backordered and will ship as soon as it is back in stock.
Product Details
This Water Pump Repair Kit – Fits Yamaha 25/30 HP Outboard Motors (Replaces 6J8-W0078-A2-00) is engineered for Yamaha 25 HP (1999, 2001–2002) & 30 HP (1997–1999, 2001–2002) 2-Stroke outboard motors. It provides all essential components to restore your engine's cooling system performance.
It serves as a direct interchange for Yamaha 6J8-W0078-A2-00, 6J8-W0078-A1-00, 6J8-W0078-C2-00, Mercury 879136, Sierra 18-3430, and GLM 12285/12284.
- Installation Location: Mounts in the lower unit.
- Fitment: Direct replacement fit.
- Important Note: The kit does not include the water pump housing unless specifically noted.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 6J8-W0078-A2-00 |
| Yamaha | 6J8-W0078-A1-00 |
| Yamaha | 6J8-W0078-C2-00 |
| Mercury | 879136 |
| Sierra | 18-3430 |
| GLM | 12285 |
| GLM | 12284 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Yamaha engines, this kit fits various 25 HP and 30 HP models from the late 1980s through the early 2000s.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 25 | 25 | 2-Stroke | 1999 | 6J8-W0078-A2-00 | |
| Yamaha | 25 | 25 | 2-Stroke | 2001–2002 | 6J8-W0078-A2-00 | |
| Yamaha | 30 | 30 | 2-Stroke | 1997–1999 | 6J8-W0078-A2-00 | |
| Yamaha | 30 | 30 | 2-Stroke | 2001–2002 | 6J8-W0078-A2-00 | |
| Yamaha | 30 | 30 | 2-Stroke | 1987, 1989–1993, 1996 | 6J8-W0078-A1-00 | Japanese Engine |
Technical Specs
- Product Type
- Water Pump Repair Kit
- Installation
- Lower Unit
- Fitting Type
- Direct Fit
- Other Technical Attributes
- Kit does not include housing unless specifically noted
What’s in the Box
- 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 Gasket, Cartridge (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)
Installation Notes
- Disconnect the battery and shift the outboard into neutral.
- Remove the lower unit (gearcase) from the outboard's midsection, placing it on a stable workbench.
- Unbolt and remove the water pump housing, taking note of the order of all components.
- Remove the old impeller, gaskets, plates, and seals.
- Thoroughly clean all mating surfaces, ensuring they are free of old gasket material and corrosion.
- Install the new components from the kit in the reverse order of disassembly. Apply a light coat of marine grease to the new impeller and inside the housing.
- Ensure the impeller vanes are oriented correctly (typically by turning the driveshaft clockwise during installation).
- Reinstall the water pump housing and torque the bolts to the manufacturer's specifications.
- Reattach the lower unit, carefully aligning the driveshaft, shift shaft, and water tube.
- Reconnect the battery and test the engine on a water source (flushing attachment or test tank) to confirm proper water flow from the tell-tale port.
Troubleshooting & FAQ
How do I know if this kit fits my specific engine model?
Verify your engine's model, horsepower, and year against the "Engine & Model Compatibility" table. For the most accurate match, cross-reference your existing part number with our "Part Number Matrix."
What are the signs of a failing water pump?
Common indicators include a weak or intermittent water stream from the engine's "tell-tale" port, engine overheating alarms, or a discovery of a brittle, cracked, or melted impeller during routine inspection.
How often should the water pump impeller be replaced?
For preventative maintenance, we recommend inspecting and replacing the impeller every 1-2 years or every 100-200 hours of operation. Service intervals should be shorter in saltwater or silty/sandy conditions.
Does this kit include the water pump housing?
No, this is a repair kit containing the impeller and related gaskets, plates, and hardware. The housing is not included unless explicitly listed in the "What's in the Box" section.
Why are there two different sets of bolts included?
Manufacturers may use different length bolts across various model years and production runs. This kit includes the most common variations to ensure you have the correct hardware for your specific lower unit.
What is the difference between OEM and aftermarket parts?
This listing is for an aftermarket replacement part, not an original equipment manufacturer (OEM) component. It is built to meet or exceed OEM-level specifications with comparable materials. Our parts are manufactured in an ISO 9002 certified facility and are batch-inspected for quality and consistency.
How fast is shipping?
We ship worldwide, with typical transit times of 5–15 days for most regions. Standard shipping is free, and expedited options are available at checkout 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 an issue, please contact our support team with your order details. Returns are accepted within our standard window for unused items in their original condition. Please see our full policy page or contact us for instructions.
Safety & Important Info
- Verify images and specifications against your original part before ordering. If anything differs—even if your model is listed as compatible—do not purchase.
- This is an aftermarket replacement part, not an OEM component.
- Professional installation is highly recommended for safety, proper function, and to prevent engine damage.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world reliability.
- Fast Global Fulfillment — We offer free standard delivery to most regions worldwide, typically arriving in 5–15 days.
- Manufacturer-Direct Value — By working directly with manufacturers, we provide fair pricing without ever compromising on materials or quality control.
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