Water Pump Impeller Repair Kit for Mercury, Tohatsu and Nissan 4–6 HP 4-Stroke Outboards
Water Pump Impeller Repair Kit for Mercury, Tohatsu and Nissan 4–6 HP 4-Stroke Outboards is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
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Water Pump Impeller Repair Kit for Mercury, Tohatsu and Nissan 4–6 ...
Water Pump Impeller Repair Kit for Mercury, Tohatsu and Nissan 4–6 HP 4-Stroke Outboards is backordered and will ship as soon as it is back in stock.
Product Details
This water pump impeller repair kit is intended for selected Mercury, Tohatsu, and Nissan 4 HP, 5 HP, and 6 HP 4-stroke outboard motors. It supplies the primary replacement components needed to service the water pump and help restore proper cooling-system performance.
The kit is listed as a replacement for the reference numbers shown below, including Mercury 16159A03 and 16159A1, and Nissan/Tohatsu 369-87322-1. Always compare the part number, engine model, and component configuration before ordering.
- Replacement water pump impeller service kit for selected small outboards.
- Includes an impeller, wear plate, gasket, and woodruff key.
- Designed to help restore water-pump sealing and cooling performance after servicing.
- Aftermarket replacement component; not an OEM-manufactured part.
Part Number Matrix
The following numbers are reference or cross-reference numbers associated with this replacement kit. Confirm the number on your original component and verify the complete engine application before installation.
| Brand or Source | Reference Number |
|---|---|
| Mercury | 16159A03 |
| Mercury | 16159A1 |
| Nissan/Tohatsu | 369-87322-1 |
| Nissan/Tohatsu | 369873221M |
| Nissan/Tohatsu | 369873221 |
| QuickMariner | 16159A1 |
| Fridayparts | FPCY2406504 |
Engine and Model Compatibility
The applications below represent the listed compatibility range for this replacement kit. Model designations, production changes, and serial-number breaks can affect fitment. Verify your exact engine model and the reference number of the original water-pump components before purchase.
Mercury 4-Stroke Outboards
| Brand | Model or Rating | Rated HP | Stroke | Year or Serial Range | Reference Part Number |
|---|---|---|---|---|---|
| Mercury | 4 HP | 4 | 4-Stroke | Not specified | 16159A03 / 16159A1 |
| Mercury | 5 HP | 5 | 4-Stroke | Not specified | 16159A03 / 16159A1 |
| Mercury | 6 HP | 6 | 4-Stroke | Not specified | 16159A03 / 16159A1 |
Tohatsu 4-Stroke Outboards
| Brand | Model | Rated HP | Stroke | Year or Serial Range | Reference Part Number |
|---|---|---|---|---|---|
| Tohatsu | M4C | 4 | 4-Stroke | Not specified | 369-87322-1 |
| Tohatsu | M5B, M5BS | 5 | 4-Stroke | Not specified | 369-87322-1 |
| Tohatsu | MFS4B, MFS4C | 4 | 4-Stroke | Not specified | 369-87322-1 |
| Tohatsu | MFS5B, MFS5C | 5 | 4-Stroke | Not specified | 369-87322-1 |
| Tohatsu | MFS6B, MFS6C | 6 | 4-Stroke | Not specified | 369-87322-1 |
Nissan 4-Stroke Outboards
| Brand | Model | Rated HP | Stroke | Year or Serial Range | Reference Part Number |
|---|---|---|---|---|---|
| Nissan | NS4C | 4 | 4-Stroke | Not specified | 369-87322-1 |
| Nissan | NS5B, NS5BS | 5 | 4-Stroke | Not specified | 369-87322-1 |
| Nissan | NSF4B, NSF4C | 4 | 4-Stroke | Not specified | 369-87322-1 |
| Nissan | NSF5B, NSF5C | 5 | 4-Stroke | Not specified | 369-87322-1 |
| Nissan | NSF6B, NSF6C | 6 | 4-Stroke | Not specified | 369-87322-1 |
Technical Specifications
- Product Type
- Water pump impeller repair kit
- Application
- Selected Mercury, Tohatsu, and Nissan 4–6 HP 4-stroke outboards
- Installation
- Direct replacement when the engine application and reference number match
- Drive Connection
- Water-pump impeller installed on the drive shaft
- Included Service Components
- Impeller, wear plate, gasket, and woodruff key
- Product Status
- Aftermarket replacement; not an OEM component
- Warranty
- 1 year against manufacturing defects under normal use, subject to applicable warranty terms
What's in the Box
- 1 × Water pump impeller
- 1 × Wear plate
- 1 × Gasket
- 1 × Woodruff key
Installation Notes
- Disconnect the battery and remove the engine cover. Follow the service precautions in the engine manufacturer's manual.
- Drain the lower-unit gear lubricant if required for removal of the gearcase.
- Remove the propeller and unbolt the lower unit from the upper leg.
- Lower the gearcase carefully, disconnecting the shift shaft or other connections as required by the engine design.
- Locate and remove the water-pump housing.
- Remove the old impeller, wear plate, gasket, and key. Note the original orientation of each component.
- Clean the mating surfaces and remove old gasket material, debris, and corrosion.
- Install the replacement gasket, wear plate, and woodruff key in the correct positions.
- Install the new impeller on the drive shaft. Rotate the shaft in the manufacturer's specified direction while seating the impeller so the vanes are oriented correctly.
- Install the pump housing and tighten its fasteners to the manufacturer's specified torque.
- Reinstall the lower unit, aligning the drive shaft, shift shaft, and water tube correctly.
- Refill the gear lubricant if it was drained, reinstall the propeller, and test the engine with an appropriate water supply. Confirm a strong cooling-water telltale stream before normal operation.
Installation procedures and shaft-rotation direction can vary by engine. Use the service manual for the exact model and do not operate the engine without an adequate water supply.
Troubleshooting and FAQ
How do I know if the water-pump impeller needs replacing?
Common signs include a weak or inconsistent telltale stream, an overheating warning, reduced water pressure, or visible impeller damage. Replace the impeller according to the maintenance schedule for your engine and inspect the wear plate and pump housing during service.
Will this kit fit my specific year and model?
The listed application range covers selected Mercury, Tohatsu, and Nissan 4–6 HP 4-stroke outboards. Year and serial-number information is not specified for this listing, so compare your exact model, serial range, original part number, and component dimensions before ordering.
What is a common installation mistake?
Installing the impeller vanes in the wrong orientation or failing to align the woodruff key can cause poor water-pump performance or premature failure. Follow the exact shaft-rotation direction and installation procedure in the engine service manual.
Should I use grease or lubricant during installation?
Use only a lubricant recommended by the engine or water-pump manufacturer. A suitable marine lubricant or a water-based solution may be used where specified to protect the impeller during initial start-up. Do not use a petroleum product if the service manual prohibits it.
The new impeller looks larger or stiffer than the old one. Is that normal?
A worn impeller may shrink, deform, or harden, so a new impeller can appear larger or stiffer. Confirm that the replacement matches the applicable reference number and seats correctly in the pump housing before assembly.
Why replace the complete kit instead of only the impeller?
The wear plate and gasket affect pump sealing and performance and may be grooved, scored, or compressed after use. Replacing the listed service components together helps restore the water-pump assembly when the original parts show wear.
Is this an OEM part?
No. This is an aftermarket replacement kit intended to replace the listed reference applications. It is not manufactured by Mercury, Tohatsu, or Nissan.
What are the shipping and return terms?
Shipping availability, delivery estimates, and return eligibility depend on the destination and the applicable order policy. Review the options shown at checkout and keep the parts unused and in their original condition if a return is required.
Safety and Important Information
- Verify the engine brand, exact model, stroke type, year or serial range, and reference number before ordering.
- Do not rely on horsepower alone to confirm fitment.
- Compare the replacement components with the original parts before installation. Do not install a component that differs in size, shape, or key configuration.
- Always use the engine manufacturer's service manual for torque values, shaft direction, gearcase removal, and cooling-system testing.
- This is an aftermarket replacement kit, not an OEM component.
- Professional installation is recommended if you are not experienced with outboard gearcase or water-pump service.
About Sea Sierra
- Pro-Grade Standards — We supply marine replacement parts selected for dependable service in real-world operating conditions.
- Global Fulfillment — Shipping options and delivery estimates are shown according to destination and availability.
- Manufacturer-Direct Value — We aim to provide practical replacement solutions with clear application and installation information.
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