Water Pump Repair Kit – Fits Yamaha 50HP-70HP Outboards (Replaces 6H3-W0078-02-00)
Water Pump Repair Kit – Fits Yamaha 50HP-70HP Outboards (Replaces 6H3-W0078-02-00) 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 Water Pump Repair Kit – Fits Yamaha 50HP-70HP Outboards (Replaces 6H3-W0078-02-00) provides all necessary components to restore your engine's cooling system. It is designed for Yamaha 4-stroke 50HP, 60HP, and 70HP outboards from 1997 and newer, including specific T50 high-thrust models.
The kit serves as a direct replacement for Yamaha OEM part 6H3-W0078-02-00 and Sierra aftermarket part 18-3465.
- Installs as a direct replacement for the original lower unit water pump.
- Includes a new impeller, gaskets, plate, and hardware for a complete overhaul.
- Engineered to meet or exceed original equipment specifications for reliable performance.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 6H3-W0078-02-00 |
| Sierra | 18-3465 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This kit is verified for the following Yamaha outboard models. Ensure your specific model and year are listed.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | F50 | 50 | 4-Stroke | 1997–newer | 6H3-W0078-02-00 | |
| Yamaha | F60 | 60 | 4-Stroke | 1997–newer | 6H3-W0078-02-00 | |
| Yamaha | F70 | 70 | 4-Stroke | 1997–newer | 6H3-W0078-02-00 | |
| Yamaha | T50 | 50 | 4-Stroke | 2006–newer | 6H3-W0078-02-00 | High thrust models |
Technical Specs
- Product Type
- Water Pump Repair Kit
- Installation
- Direct replacement
- Dimensions
- 10.0"L x 10.0"W x 5.5"H
- Other Technical Attributes
- Designed for Yamaha outboard lower units
What’s in the Box
- 1 x Cartridge Insert (663-44322-00-00)
- 1 x Impeller (6H3-44352-00-00)
- 1 x Water Pump Gasket 1 (6H3-44315-A0-00)
- 1 x Cartridge Outer Plate (6H3-44323-00-00)
- 1 x Cartridge Gasket (6H3-44324-A0-00)
- 1 x Water Pump Gasket 2 (688-44316-A0-00)
- 1 x O-Ring (93210-46044-00)
- 2 x Bolt, With Washer (90119-08M14-00)
- 2 x Bolt, With Washer (90119-08M33-00)
- 1 x Woodruff Key (90280-03M03-00)
Installation Notes
- Disconnect the battery leads and shift the engine into neutral.
- Place a drain pan under the lower unit and remove the gearcase oil drain screw to empty the oil.
- Unbolt and carefully separate the lower unit (gearcase) from the upper engine housing.
- Remove the bolts securing the water pump housing and lift it off the driveshaft.
- Remove the old impeller, gaskets, wear plate, and any remaining components from the kit.
- Thoroughly clean all mating surfaces, ensuring they are free of old gasket material and corrosion.
- Install the new components from the kit in reverse order, starting with the Woodruff key and impeller.
- Lubricate the inside of the new housing and impeller with grease before reassembly.
- Torque all bolts to the manufacturer's specified values.
- Reinstall the lower unit, refill the gearcase oil with the correct type and amount, and test the engine using a water supply (flusher).
Troubleshooting & FAQ
How do I know if this kit fits my Yamaha engine?
This kit is designed for specific Yamaha 50HP, 60HP, 70HP, and T50 outboards. The best way to confirm is by matching your engine's model and year to the compatibility table. You can also cross-reference your existing part number with the ones listed in the Part Number Matrix.
What are the common signs of a failing water pump?
A weak or intermittent water stream from the "telltale" outlet is the most common sign. Other symptoms include the engine overheating alarm sounding, steam from the exhaust, or reduced engine performance.
How often should I service the water pump?
As a general maintenance guideline, inspect the impeller annually and replace the entire water pump kit every 2-3 years or 200-300 hours of use, whichever comes first. Usage in saltwater or sandy/murky water may require more frequent service.
Is the impeller difficult to install on the driveshaft?
The impeller must be installed with the vanes pointing in the correct rotational direction. Apply a bit of marine grease to the inside of the pump housing and slide the housing down over the impeller while turning the driveshaft clockwise to help fold the vanes correctly.
What if my engine still overheats after installing the new kit?
If overheating persists, the issue may be a blockage in the cooling water passages, a stuck thermostat, or a faulty temperature sensor. Systematically check these other components after confirming the water pump is installed correctly and functioning.
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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