Water Pump Impeller Kit – Fits Yamaha 25-40HP 4-Stroke Outboards (Replaces 66T-W0078-00)
Water Pump Impeller Kit – Fits Yamaha 25-40HP 4-Stroke Outboards (Replaces 66T-W0078-00) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.
Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Product Details
This aftermarket Water Pump Impeller Kit – Fits Yamaha 25-40HP 4-Stroke Outboards (Replaces 66T-W0078-00) is designed for Yamaha 4-Stroke engines from 25–40HP, model years 2000 to present. It is confirmed to fit T25, F30 (2001–2005), F40 (2000–2008), and F40B (all years) outboards, ensuring reliable performance for cooling system maintenance.
It serves as a direct interchange for Yamaha part numbers 66T-W0078-00-00 and 66T-W0078-01-00, as well as Sierra 18-3440.
- Engineered for direct OEM-replacement installation.
- Marine-rated for durability in both saltwater and freshwater environments.
- Includes the impeller, housing, gaskets, and all necessary hardware for a complete repair.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 66T-W0078-00-00 |
| Yamaha | 66T-W0078-01-00 |
| Sierra | 18-3440 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This kit is specifically designed for select Yamaha outboard models. Please verify your engine's details against this chart to ensure proper fitment.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | T25 | 25 | 4-Stroke | All years | 66T-W0078-00-00 | |
| Yamaha | F30 | 30 | 4-Stroke | 2001–2005 | 66T-W0078-00-00 | |
| Yamaha | F40 | 40 | 4-Stroke | 2000–2008 | 66T-W0078-00-00 | |
| Yamaha | F40B | 40 | 4-Stroke | All years | 66T-W0078-00-00 |
Technical Specs
- Product Type
- Water Pump Impeller Repair Kit
- Installation
- Direct OEM replacement
- Housing Material
- Metal and rubber
- Components
- Impeller, housing, gaskets, hardware
- Environment
- Marine-rated for saltwater and freshwater
- Other Technical Attributes
- Designed for extreme marine conditions
- Product Dimensions
- 10.0" L x 10.0" W x 11.5" H
- Box Dimensions
- 10.0" L x 10.0" W x 11.5" H
What’s in the Box
- 1 x Cartridge Insert (63D-44322-00-00)
- 1 x Cartridge Outer Plate (66T-44323-00-00)
- 1 x O-Ring (93210-59MG7-00)
- 1 x Water Pump Gasket (63D-44316-00-00)
- 1 x Woodruff Key (90280-03M03-00)
- 1 x Impeller (6H4-44352-02-00)
- 4 x Bolts with Washer (90119-08M15-00)
- 1 x Water Seal Damper 2 (663-44366-00-00)
- 1 x Pump Housing Cover (63D-44312-00-00)
Installation Notes
- Disconnect the battery and spark plug leads for safety.
- Drain the lower unit gear oil into a suitable container.
- Remove the mounting bolts securing the lower unit (gearcase) to the engine.
- Carefully lower the gearcase away from the midsection.
- Unbolt and remove the old water pump housing assembly.
- Remove the old impeller, gaskets, plates, and seals. Clean all mating surfaces thoroughly.
- Install the new gasket, wear plate, impeller, and Woodruff key. Ensure the impeller vanes are oriented correctly.
- Fit the new housing and seals, tightening bolts to the manufacturer's specified torque.
- Re-install the lower unit, ensuring the driveshaft and water tube align.
- Refill the gearcase with fresh marine gear oil.
- Reconnect the battery and test engine operation in a safe water environment, verifying water output.
Troubleshooting & FAQ
How can I tell if my water pump impeller is failing?
Common signs of a worn or failed impeller include a weak or intermittent water stream from the tell-tale port, engine overheating alarms, and in severe cases, visible steam from the exhaust. It's crucial to address these symptoms immediately to prevent engine damage.
What is the recommended replacement interval for this kit?
For optimal performance and engine safety, most marine technicians recommend inspecting the water pump impeller annually and replacing it every 1-2 years or every 100-200 hours of operation, depending on usage conditions (e.g., saltwater vs. freshwater).
Is this kit compatible with a Yamaha F40B from any year?
Yes, our compatibility data confirms that this water pump repair kit fits all model years of the Yamaha F40B 4-stroke outboard. Always double-check your OEM part number to be certain.
Do I need to buy any other components for the installation?
This kit is designed to be comprehensive, including the impeller, housing, gaskets, plates, and bolts. In most cases, you will not need additional parts. However, we recommend having marine-grade grease and new lower unit gear oil on hand for the reassembly process.
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/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
Payment & Security
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