Water Pump Impeller Service Kit for Mercury/Mariner and Tohatsu 2.5–3.5 HP 4-Stroke Outboards – Replaces 8M0181314, 47-161543, 369-65021-1 and 309-65021-1
Water Pump Impeller Service Kit for Mercury/Mariner and Tohatsu 2.5–3.5 HP 4-Stroke Outboards – Replaces 8M0181314, 47-161543, 369-65021-1 and 309-65021-1 is backordered and will ship as soon as it is back in stock.
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Water Pump Impeller Service Kit for Mercury/Mariner and Tohatsu 2.5...
Water Pump Impeller Service Kit for Mercury/Mariner and Tohatsu 2.5–3.5 HP 4-Stroke Outboards – Replaces 8M0181314, 47-161543, 369-65021-1 and 309-65021-1 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket water pump impeller service kit is intended for selected Mercury/Mariner and Tohatsu 2.5 HP and 3.5 HP 4-stroke outboard applications. The Mercury/Mariner applications are Tohatsu-based engines, so confirm the exact model and serial-number range before ordering.
The kit is associated with Mercury references 8M0181314 and 47-161543, plus Tohatsu references 369-65021-1 and 309-65021-1. These numbers are included as identification and cross-reference information; always compare the original impeller and the engine parts diagram before installation.
- Includes an impeller, water-pump gaskets, an impeller key and two gearbox drain/fill screw fibre washers.
- Designed for routine water-pump service on compatible small outboards.
- Suitable for freshwater and saltwater service when installed and maintained correctly.
- Aftermarket replacement; not an original Mercury, Mariner or Tohatsu-branded kit.
Part Number Matrix
Use the following references to compare the replacement with the part listed for your engine.
| Brand | Reference | Role |
|---|---|---|
| Mercury | 8M0181314 | Service-kit reference |
| Mercury | 47-161543 | Impeller/service reference |
| Tohatsu | 369-65021-1 | Water-pump impeller reference |
| Tohatsu | 309-65021-1 | Water-pump impeller reference used in other applications |
Engine & Model Compatibility
Fitment must be confirmed by engine brand, model, horsepower, stroke and serial number together. The references above also appear in other Tohatsu applications, including some 2-stroke models, so a part-number match by itself is not sufficient.
| Brand | Model family | Rated HP | Stroke | Application notes | Related reference |
|---|---|---|---|---|---|
| Mercury/Mariner | F2.5 | 2.5 | 4-Stroke | Selected Tohatsu-manufactured applications; verify serial number before purchase. | 8M0181314 / 47-161543 |
| Mercury/Mariner | F3.5 | 3.5 | 4-Stroke | Selected Tohatsu-manufactured applications; verify serial number before purchase. | 8M0181314 / 47-161543 |
| Tohatsu | MFS2.5 / MFS3.5 | 2.5 / 3.5 | 4-Stroke | Catalog occurrences identify the impeller reference in the MFS2/MFS2.5/MFS3.5B family. Confirm the exact year and parts diagram. | 369-65021-1 |
Important: Do not use this listing for a 2-stroke engine unless your engine's parts diagram specifically confirms the same complete service-kit contents and application. The same impeller references are cataloged across multiple engine families with different fitment conditions.
Technical Specifications
- Product Type
- Aftermarket water pump impeller service kit
- Primary Service
- Outboard lower-unit water-pump maintenance
- Impeller Material
- Neoprene rubber with a molded hub
- Impeller Reference
- 369-65021-1 / 309-65021-1
- Installation
- Replacement installation using standard marine service tools
- Fitment Type
- Application-specific aftermarket replacement
- Stroke Coverage
- 4-stroke Mercury/Mariner and Tohatsu applications listed above; verify before ordering
What's in the Box
- 1 x Water pump impeller
- 1 x Water pump gasket, reference 3F0-65018-0
- 1 x Water pump gasket, reference 3F0-65029-0
- 1 x Impeller key, reference 369-65022-0
- 2 x Gearbox drain/fill screw fibre washers, reference 332-60006-0
Installation Notes
- Disconnect the spark-plug lead and follow the engine manufacturer's safety instructions.
- Place a drain pan under the gearcase. Remove the drain and fill screws and drain the gear oil if required by the service procedure.
- Remove the bolts securing the lower unit to the midsection and carefully lower the unit.
- Remove the water-pump housing to expose the old impeller.
- Clean the housing, base plate and mating surfaces. Remove all old gasket material and debris.
- Install the new key, gaskets and impeller in the correct order. Follow the engine service manual for vane orientation and tightening torque.
- Reinstall the pump housing and lower unit. Refill the gearcase with the specified lubricant and inspect the screw washers for proper sealing.
- Run the engine only in water or with an appropriate flushing device, then confirm a steady tell-tale stream and check for leaks or overheating.
Installation warning: Incorrect impeller orientation, missing gaskets, debris in the pump housing or running the engine without a water supply can cause overheating and engine damage.
Troubleshooting & FAQ
How do I confirm fitment for my engine?
Check the brand, exact model designation, horsepower, stroke and serial number against the engine parts diagram. For the listed Mercury/Mariner and Tohatsu 4-stroke applications, also compare the original impeller and the applicable reference number before ordering.
Does this kit fit every 2.5 HP or 3.5 HP outboard?
No. Horsepower alone does not confirm fitment. The same or related impeller references appear in multiple Tohatsu model families and in both 2-stroke and 4-stroke catalog applications. Confirm the complete engine identification and service-kit contents.
When should the water-pump impeller be replaced?
Replace it according to the engine manufacturer's maintenance schedule and inspect it whenever cooling-water flow is weak, the tell-tale stops flowing, or an overheating warning occurs. Replace it sooner after operation in sand, silt or heavy saltwater exposure.
What are the signs of a worn or damaged impeller?
Common signs include a weak or absent tell-tale stream, overheating, an overheating alarm or visible cracking and deformation when the pump is inspected. Stop operating the engine if cooling flow is abnormal.
Is this an OEM kit?
No. This is an aftermarket replacement kit supplied for compatible applications. The Mercury, Mariner and Tohatsu references are shown for identification and cross-reference purposes.
What is included compared with an original service kit?
This listing includes the impeller, listed water-pump gaskets, impeller key and two gearbox drain/fill screw fibre washers. Contents of original-branded service kits may differ, so compare the package list before ordering.
How should I store the replacement impeller?
Keep it sealed, clean and away from direct sunlight, ozone, petroleum products and excessive heat until installation. Do not install an impeller that is cracked, permanently deformed or contaminated.
Safety & Important Information
- Verify the engine's exact model, year or production range, stroke and serial number before purchase.
- Compare the original part and all kit components with the package list.
- Never run an outboard without an adequate water supply.
- Use the engine service manual for torque values, gear-oil requirements and final testing.
- Professional installation is recommended when lower-unit service is unfamiliar.
- This is an aftermarket replacement and is not manufactured or packaged by Mercury, Mariner or Tohatsu.
About Sea Sierra
- Marine replacement parts — Practical components for routine maintenance and repair.
- Application-focused listings — Product references and fitment conditions are provided to help customers compare before ordering.
- Support for maintenance work — Always use the manufacturer's service information for final installation and safety procedures.
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