Water Pump Impeller with Key – Fits Tohatsu/Nissan 2–5 HP 2-Stroke, MFS4–6 HP 4-Stroke and Mercury/Mariner 2–3.5 HP 4-Stroke
Water Pump Impeller with Key – Fits Tohatsu/Nissan 2–5 HP 2-Stroke, MFS4–6 HP 4-Stroke and Mercury/Mariner 2–3.5 HP 4-Stroke is backordered and will ship as soon as it is back in stock.
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Water Pump Impeller with Key – Fits Tohatsu/Nissan 2–5 HP 2-Stroke,...
Water Pump Impeller with Key – Fits Tohatsu/Nissan 2–5 HP 2-Stroke, MFS4–6 HP 4-Stroke and Mercury/Mariner 2–3.5 HP 4-Stroke is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket water pump impeller with drive key is designed to help maintain proper cooling-water circulation in compatible small outboard engines. It is listed for selected Nissan and Tohatsu 2-stroke models from 2 to 5 HP, Tohatsu MFS4–6 HP 4-stroke models, and selected Mercury/Mariner 2–3.5 HP carbureted 4-stroke models.
The impeller is supplied with the key required for installation. Confirm your exact engine model, stroke, and existing impeller dimensions before ordering.
- Six-blade water pump impeller with included drive key.
- Direct replacement design for compatible water pump assemblies.
- Approximate dimensions: 10.25 mm inside diameter, 33.6 mm outside diameter, and 14.2 mm width.
- For cooling-system service on compatible small outboard engines.
Part Number Matrix
Use these manufacturer and aftermarket reference numbers to help identify the correct replacement. Numbers are provided for identification and compatibility checking.
| Brand or Source | Reference Number |
|---|---|
| Tohatsu | 369-65021-1 |
| Tohatsu catalog reference | 369650211M |
| Mercury/Mariner | 47-16154-3 |
| Sierra | 18-3098 |
| Mallory | 9-45302 |
| CEF | 500377 |
Engine & Model Compatibility
The applications below reflect the available product fitment records. Model, stroke, and horsepower conditions must be considered together. Do not rely on horsepower alone to confirm fitment.
Tohatsu and Nissan 2-Stroke Applications
| Brand | Model or Description | Rated HP | Stroke | Reference |
|---|---|---|---|---|
| Tohatsu/Nissan | 2 HP models | 2 | 2-Stroke | 369-65021-1 |
| Tohatsu/Nissan | 2.5 HP models | 2.5 | 2-Stroke | 369-65021-1 |
| Tohatsu/Nissan | M2.5A, M3.5A, M3.5B and related 2.5–3.5 HP models | 2.5–3.5 | 2-Stroke | 369-65021-1 |
| Tohatsu/Nissan | 3.5 HP models | 3.5 | 2-Stroke | 369-65021-1 |
| Tohatsu/Nissan | 4–5 HP models | 4–5 | 2-Stroke | 369-65021-1 |
| Nissan | 3.5B / NS5B | 3.5–5 | 2-Stroke | 369-65021-1 |
Tohatsu 4-Stroke Applications
| Brand | Model | Rated HP | Stroke | Reference |
|---|---|---|---|---|
| Tohatsu | MFS4 | 4 | 4-Stroke | 369-65021-1 |
| Tohatsu | MFS5 | 5 | 4-Stroke | 369-65021-1 |
| Tohatsu | MFS6 | 6 | 4-Stroke | 369-65021-1 |
Mercury/Mariner 4-Stroke Applications
| Brand | Model or Description | Rated HP | Stroke | Condition | Reference |
|---|---|---|---|---|---|
| Mercury/Mariner | 2 HP | 2 | 4-Stroke | Carbureted models | 47-16154-3 |
| Mercury/Mariner | 2.5 HP | 2.5 | 4-Stroke | Carbureted models | 47-16154-3 |
| Mercury/Mariner | 3.5 HP | 3.5 | 4-Stroke | Carbureted models | 47-16154-3 |
Fitment note: The compatibility records do not establish universal fitment across every engine in the same horsepower range. Check the full model designation and compare the original impeller dimensions before installation.
Technical Specs
- Product Type
- Water pump impeller with drive key
- Application
- Cooling-system replacement for compatible small outboard engines
- Number of Blades
- 6
- Inside Diameter
- 10.25 mm
- Outside Diameter
- 33.6 mm
- Width
- 14.2 mm
- Installation
- Direct replacement in a matching water pump assembly
What's in the Box
- 1 x Six-blade water pump impeller
- 1 x Drive key
Installation Notes
- Disconnect the battery and remove the spark plug wire or wires before servicing the outboard.
- Place the engine in neutral and remove the fasteners securing the lower unit or gearcase.
- Separate the lower unit carefully, paying attention to the shift shaft and driveshaft alignment.
- Remove the water pump housing cover and take out the old impeller and drive key.
- Clean debris from the housing and inspect the housing, wear plate, seals, and keyway for damage or excessive wear.
- Install the supplied key and impeller in the correct orientation. Use a suitable water-pump lubricant during assembly and rotate the driveshaft in the normal direction of operation as the impeller enters the housing.
- Reinstall the housing and any removed gaskets or seals according to the engine manufacturer's service procedure.
- Reassemble the lower unit and test the cooling-water flow using an appropriate water supply before returning the engine to service.
Troubleshooting & FAQ
How do I know if my impeller is failing?
Common warning signs include weak or missing water flow from the tell-tale outlet, overheating, an overheat alarm, or visible cracks, deformation, or missing blades during inspection.
Does this product include the drive key?
Yes. This listing is for a water pump impeller supplied with a drive key. Confirm that the keyway and impeller dimensions match your original components before installation.
Will this fit any 2–6 HP outboard?
No. Horsepower by itself does not confirm fitment. This product is listed for the specific Tohatsu, Nissan, and Mercury/Mariner model groups shown above. Check the exact model, stroke type, and dimensions before ordering.
What is the difference between this impeller and the OEM version?
This is an aftermarket replacement impeller, not an original manufacturer-supplied component. It is intended for applications using the listed reference numbers and matching dimensions.
How often should a water pump impeller be replaced?
Inspect the impeller as part of regular maintenance and replace it when the blades show wear, cracking, distortion, or damage. Follow the service interval recommended for your specific engine and operating conditions.
Safety & Important Information
- Verify the exact engine model, stroke type, reference number, and dimensions before purchase.
- All brand names and reference numbers are used only to identify compatible applications; this product is aftermarket and is not an OEM component.
- Do not operate an outboard with inadequate cooling-water flow. Stop the engine immediately if overheating or a loss of tell-tale flow occurs.
- Professional installation is recommended when you are not familiar with lower-unit or water-pump service.
About Sea Sierra
Sea Sierra supplies aftermarket marine replacement parts for maintenance and repair applications. Product compatibility should always be confirmed against the engine's exact model information and the original part before installation.
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