Water Pump Impeller Repair Kit – Fits Mercury/Tohatsu/Nissan 4-6HP Outboards (Replaces 369-87322-1)
Water Pump Impeller Repair Kit – Fits Mercury/Tohatsu/Nissan 4-6HP Outboards (Replaces 369-87322-1) 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
Free standard shipping on all orders under 1 KG
Water Pump Impeller Repair Kit – Fits Mercury/Tohatsu/Nissan 4-6HP ...
Product Details
This Water Pump Impeller Repair Kit is designed for Mercury, Tohatsu, and Nissan 4HP, 5HP, and 6HP 4-stroke outboard motors. It provides all the necessary components for a complete water pump service to restore cooling system performance and prevent engine overheating.
It serves as a direct replacement for multiple OEM and aftermarket part numbers, including Mercury 16159A03/16159A1, Nissan/Tohatsu 369-87322-1, and others, ensuring broad compatibility.
- Engineered for direct-fit installation on the drive shaft.
- Includes a new impeller and essential replacement components for a full repair.
- Restores cooling efficiency and protects the engine from damage due to a failed impeller.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 16159A03 |
| Mercury | 16159A1 |
| Nissan/Tohatsu | 369-87322-1 |
| Nissan/Tohatsu | 369873221M |
| Nissan/Tohatsu | 369873221 |
| QuickMariner | 16159A1 |
| Fridayparts | FPCY2406504 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
Fits select Mercury 4-stroke outboards from 4HP to 6HP.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| Mercury | 4HP | 4 | 4-Stroke | 16159A03/16159A1 | |
| Mercury | 5HP | 5 | 4-Stroke | 16159A03/16159A1 | |
| Mercury | 6HP | 6 | 4-Stroke | 16159A03/16159A1 |
Fits various Tohatsu 4-stroke models including M4C, M5B, MFS4B/C, MFS5B/C, and MFS6B/C series.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| Tohatsu | M4C | 4 | 4-Stroke | 369-87322-1 | |
| Tohatsu | M5B, M5BS | 5 | 4-Stroke | 369-87322-1 | |
| Tohatsu | MFS4B, MFS4C | 4 | 4-Stroke | 369-87322-1 | |
| Tohatsu | MFS5B, MFS5C | 5 | 4-Stroke | 369-87322-1 | |
| Tohatsu | MFS6B, MFS6C | 6 | 4-Stroke | 369-87322-1 |
Fits Nissan 4-stroke equivalents, including the NS4C, NS5B, NSF4B/C, NSF5B/C, and NSF6B/C series.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| Nissan | NS4C | 4 | 4-Stroke | 369-87322-1 | |
| Nissan | NS5B, NS5BS | 5 | 4-Stroke | 369-87322-1 | |
| Nissan | NSF4B, NSF4C | 4 | 4-Stroke | 369-87322-1 | |
| Nissan | NSF5B, NSF5C | 5 | 4-Stroke | 369-87322-1 | |
| Nissan | NSF6B, NSF6C | 6 | 4-Stroke | 369-87322-1 |
Technical Specs
- Product Type
- Water Pump Impeller Repair Kit
- Installation
- Direct replacement
- Connection
- Direct drive shaft connection
- Fitting Type
- Direct fit on drive shaft
- Warranty
- 1 year (Fridayparts)
- Other Technical Attributes
- Includes impeller and necessary replacement components
What’s in the Box
- 1 x Impeller
- 1 x Wear Plate
- 1 x Gasket
- 1 x Woodruff Key
Installation Notes
- Disconnect the battery and remove the engine cover.
- Drain the lower unit gear lube.
- Remove the propeller and unbolt the lower unit (gearcase) from the upper leg.
- Carefully lower the gearcase, disconnecting the shift shaft if necessary.
- Locate and unbolt the water pump housing.
- Remove the old impeller, plate, and gaskets. Note their orientation.
- Clean all mating surfaces thoroughly, removing any old gasket material or corrosion.
- Install the new gasket, wear plate, and woodruff key on the driveshaft.
- Slide the new impeller onto the driveshaft, turning the shaft clockwise to bend the vanes correctly.
- Install the new housing and torque bolts to manufacturer specifications.
- Reassemble the lower unit to the engine leg, ensuring the driveshaft, shift shaft, and water tube are correctly aligned.
- Refill the gear lube, reinstall the propeller, and test run the engine with a water supply, checking for proper water output.
Troubleshooting & FAQ
How do I know if my water pump impeller needs replacing?
Common signs of a failing impeller include a weak or inconsistent water stream from the "telltale" outlet, engine overheating alarms, or a visible decrease in water pressure. It is recommended to replace the impeller as part of regular maintenance every 1-2 years or every 100-200 hours of use, regardless of visible wear.
Will this kit fit my specific year and model?
This kit is designed for Mercury, Tohatsu, and Nissan 4-6HP 4-stroke outboards. While year ranges are broad, it is critical to verify your engine's part number against the provided Part Number Matrix. If you are unsure, consult your owner's manual or a qualified marine mechanic.
What is the most common installation mistake?
The most frequent error is installing the impeller with the vanes bent in the wrong direction. Always turn the driveshaft clockwise while pushing the impeller down into the housing to ensure the vanes curve correctly against the direction of rotation. Installing it backwards will result in poor performance and rapid failure.
Is any special grease needed during installation?
Yes, it's highly recommended to use a light coat of marine-grade grease or a soapy water solution on the inside of the pump housing and on the impeller vanes. This provides lubrication during the initial dry startup before water reaches the pump, preventing damage.
The new impeller seems slightly larger than the old one. Is this normal?
Yes, a new impeller may appear slightly larger or stiffer than a worn one. The old impeller can shrink, deform, and harden over time. The new impeller is designed for a snug fit inside the housing to create proper pressure. As long as it matches the cross-reference part number, it should fit correctly.
What happens if I don't replace the whole kit and just the impeller?
While you can sometimes replace only the impeller, it is not recommended. The wear plate and housing can develop grooves and scoring over time, which will reduce water pressure and prematurely wear out a new impeller. Using the full kit ensures all sealing surfaces are fresh for optimal, long-lasting performance.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an 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.
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