Aftermarket Water Pump Impeller with Key – for Mercury Mariner 2-Stroke 3.5, 3.9, 5 & 6 HP – Replaces Mercury 47-22748
Aftermarket Water Pump Impeller with Key – for Mercury Mariner 2-Stroke 3.5, 3.9, 5 & 6 HP – Replaces Mercury 47-22748 is backordered and will ship as soon as it is back in stock.
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Aftermarket Water Pump Impeller with Key – for Mercury Mariner 2-St...
Aftermarket Water Pump Impeller with Key – for Mercury Mariner 2-Stroke 3.5, 3.9, 5 & 6 HP – Replaces Mercury 47-22748 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket water pump impeller with key is designed for selected Mercury Mariner 2-stroke outboard engines rated at 3.5, 3.9, 5, and 6 HP. It is a direct replacement for the water-pump impeller used in the engine cooling system and helps restore proper water circulation when the original impeller is worn, cracked, brittle, or damaged.
The impeller is supplied with a key and is identified as an aftermarket replacement for Mercury Marine part number 47-22748. The aftermarket reference associated with this product is 18-3012.
- Product Type: Water pump impeller with key
- Engine Type: 2-stroke outboard
- Installation Method: Direct replacement
- Application: Mercury Mariner 3.5, 3.9, 5, and 6 HP engines
- Included Components: One impeller and one key
Part Number References
Use the references below together with your engine model and original component dimensions to confirm the correct application.
| Reference Type | Brand or Catalog | Part Number |
|---|---|---|
| OEM replacement reference | Mercury Marine | 47-22748 |
| Aftermarket reference | Sierra | 18-3012 |
Engine & Model Compatibility
This product is listed for Mercury Mariner 2-stroke engines in the horsepower range shown below. Model names, production years, and serial-number ranges can vary by market and engine configuration, so compare the original impeller and verify the exact engine identification before ordering.
| Brand | Engine Rating | Stroke | Application Scope | Replacement Reference | Notes |
|---|---|---|---|---|---|
| Mercury Mariner | 3.5 HP | 2-Stroke | Selected engines | 47-22748 | Confirm the original impeller dimensions and key arrangement. |
| Mercury Mariner | 3.9 HP | 2-Stroke | Selected engines | 47-22748 | Confirm the original impeller dimensions and key arrangement. |
| Mercury Mariner | 5 HP | 2-Stroke | Selected engines | 47-22748 | Confirm the original impeller dimensions and key arrangement. |
| Mercury Mariner | 6 HP | 2-Stroke | Selected engines | 47-22748 | Catalog fitment depends on the exact model and serial-number range. |
Technical Specs
- Product Type
- Water pump impeller with key
- Replacement Type
- Aftermarket direct replacement
- Engine Type
- 2-stroke outboard
- Outside Diameter
- 1.250 in (31.75 mm)
- Inside Diameter
- 0.456 in (approximately 11.58 mm)
- Key
- Included with the product
- Installation
- Direct fit when the engine application and dimensions match
- Intended Environment
- For marine cooling-system service; always follow the engine manufacturer's maintenance and operating instructions.
What's in the Box
- 1 x Water pump impeller
- 1 x Impeller key
Installation Notes
- Stop the engine and follow all manufacturer safety procedures before beginning work.
- Remove the lower unit according to the service procedure for your specific Mercury Mariner engine.
- Remove the water-pump housing and take out the old impeller and key.
- Inspect the housing, wear plate, water tube, seals, and related components for scoring, distortion, blockage, or damage. Replace damaged parts as required.
- Install the supplied key in the driveshaft keyway and fit the new impeller in the correct position.
- Reinstall the water-pump housing, ensuring that the impeller vanes are positioned correctly as the housing is fitted.
- Reinstall the lower unit and confirm that the driveshaft and water tube are properly aligned.
- Operate the engine only in an appropriate test tank or body of water, and verify that cooling-water flow is present before normal use.
Troubleshooting & FAQ
How do I confirm that this impeller fits my engine?
Verify that your engine is a Mercury Mariner 2-stroke model in the 3.5, 3.9, 5, or 6 HP range. Then compare the original impeller's outside diameter, inside diameter, key arrangement, model identification, and serial-number range where applicable. Do not rely on horsepower alone.
What are the signs of a failing water-pump impeller?
Typical signs include overheating, reduced cooling-water flow, an intermittent or weak telltale stream, or impeller vanes that are cracked, brittle, deformed, or missing.
Does the product include the key?
Yes. The product is supplied as a water pump impeller with one key.
Is this an OEM Mercury part?
No. This is an aftermarket replacement component intended to replace the Mercury Marine 47-22748 impeller when the application and dimensions match.
Can I use this listing for a 4-stroke or 9.8 HP engine?
The company application data specifies Mercury Mariner 2-stroke engines rated at 3.5, 3.9, 5, and 6 HP. A 4-stroke or 9.8 HP engine is not confirmed for this product by the supplied company record.
How often should an outboard impeller be replaced?
Replacement timing depends on the engine manufacturer's maintenance schedule, operating hours, water conditions, and the condition of the existing impeller. Inspect the impeller during scheduled cooling-system service and replace it if wear or damage is found.
Safety & Important Information
- Confirm the exact engine model, stroke, horsepower, serial-number range where applicable, and original impeller dimensions before purchasing.
- Do not run an outboard without an adequate water supply for cooling.
- This is an aftermarket replacement component, not an original Mercury Marine part.
- If the original component differs in diameter, key arrangement, vane design, or overall profile, do not install this replacement.
- Professional installation is recommended when the water-pump assembly or lower unit is unfamiliar.
About Sea Sierra
- Marine Replacement Parts — We supply replacement components for routine marine maintenance and repair.
- Application-Focused Listings — Product descriptions emphasize engine type, application scope, and reference numbers to support part selection.
- Practical Maintenance Support — Always compare the original component and follow the service procedure for your specific engine.
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