Water Pump Impeller Kit – Fits Yamaha 25HP-40HP (Replaces 66T-W0078-A0, 18-3432, 89890)
Water Pump Impeller Kit – Fits Yamaha 25HP-40HP (Replaces 66T-W0078-A0, 18-3432, 89890) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
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Water Pump Impeller Kit – Fits Yamaha 25HP-40HP (Replaces 66T-W0078...
Water Pump Impeller Kit – Fits Yamaha 25HP-40HP (Replaces 66T-W0078-A0, 18-3432, 89890) is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket Water Pump Impeller Kit – Fits Yamaha 25HP-40HP Outboards (Replaces 66T-W0078-A0) is designed for a wide range of Yamaha 2-Stroke and 4-Stroke outboard engines from 25HP to 40HP, covering models manufactured between 1993 and 2006.
It serves as a direct interchange for Yamaha OEM part numbers 66T-W0078-A0, 66T-W0078-A0-00, 66T-W0078-00-00, and 66T-W0078-01-00, as well as aftermarket cross-references like Sierra 18-3432 and GLM 89890.
- Engineered for direct-fit installation with no modifications required.
- Kit includes the essential impeller, gaskets, and key for a complete service.
- Restores cooling system performance to prevent engine overheating and ensure reliability.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 66T-W0078-A0 |
| Yamaha | 66T-W0078-A0-00 |
| Yamaha | 66T-W0078-00-00 |
| Yamaha | 66T-W0078-01-00 |
| Sierra | 18-3432 |
| GLM | 89890 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Yamaha owners, ensure your model and year range match the specifications shown. Note the different OEM part number for the C30 model, which requires an alternative kit.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | F25 | 25 | 4-Stroke | 1998–2006 | 66T-W0078-A0 | |
| Yamaha | F30 | 30 | 4-Stroke | 2001–2006 | 66T-W0078-A0 | |
| Yamaha | F40 | 40 | 4-Stroke | 1999–2006 | 66T-W0078-A0 | |
| Yamaha | C30 | 30 | 2-Stroke | 1993–1997 | 61N-W0078-11-00 | Alternative kit |
Technical Specs
- Product Type
- Water Pump Impeller Kit
- Installation
- Direct replacement
What’s in the Box
- 1 x Impeller
- 1 x Water Pump Housing Gasket
- 1 x Wear Plate to Gear Case Mounting Gasket
- 1 x Wear Plate to Pump Housing Gasket
- 1 x Impeller Key
- Additional gaskets and O-rings may be included depending on specific kit configuration
Installation Notes
- Disconnect the battery and shift the outboard into the neutral position.
- Remove the lower unit (gearcase) by unbolting it from the engine's midsection.
- Unbolt and remove the water pump housing to access the old impeller.
- Note the rotational direction of the old impeller's vanes before removing it and the impeller key.
- Thoroughly clean all mating surfaces, removing any old gasket residue.
- Install the new impeller key, wear plate, gaskets, and impeller. Bending the new impeller vanes in the correct direction during installation is critical.
- Reassemble the pump housing and torque its bolts to the manufacturer's specified value.
- Reinstall the lower unit, carefully aligning the driveshaft, shift shaft, and water tube.
- Reconnect the battery and test the engine on a water supply, confirming a strong, steady stream from the tell-tale port.
Troubleshooting & FAQ
How do I know if this kit fits my Yamaha outboard?
This kit fits specific Yamaha 25HP to 40HP models from 1993–2006. Please verify your exact model and year in the 'Engine & Model Compatibility' table and cross-reference your OEM part number with our 'Part Number Matrix' to ensure a perfect match.
What are the signs of a failing water pump impeller?
Common signs include a weak or non-existent water stream from the "tell-tale" outlet, engine overheating alarms, and a noticeable drop in performance. A brittle, cracked, or deformed impeller upon inspection confirms failure.
The compatibility table lists an "Alternative kit" for my C30. What's the difference?
The part number 61N-W0078-11-00 listed for the C30 2-Stroke is a different kit. While this 66T-series kit may have shared components, you must purchase the exact part number specified for your engine to guarantee correct fit and function.
How often should the water pump impeller be replaced?
For preventative maintenance, we recommend replacing the impeller every 100-200 operating hours or at least once every one to two years, whichever comes first. This interval should be shorter if you frequently operate in sandy, silty, or debris-heavy water.
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 and specifications against your original part before purchase. If anything differs—even if your model is listed as compatible—do not purchase.
- This is an aftermarket replacement component, not an Original Equipment Manufacturer (OEM) part.
- Professional installation is highly recommended for safety, proper function, and engine longevity.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days, getting you back on the water faster.
- Manufacturer-Direct Value — By working directly with manufacturers, we offer fair pricing without compromising on materials or quality control.
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