Water Pump Impeller for Mercury Mariner 2-Stroke 3.9–9.8 HP Outboards – 0.456 in Shaft – Replaces 47-89981
Water Pump Impeller for Mercury Mariner 2-Stroke 3.9–9.8 HP Outboards – 0.456 in Shaft – Replaces 47-89981 is backordered and will ship as soon as it is back in stock.
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Water Pump Impeller for Mercury Mariner 2-Stroke 3.9–9.8 HP Outboar...
Water Pump Impeller for Mercury Mariner 2-Stroke 3.9–9.8 HP Outboards – 0.456 in Shaft – Replaces 47-89981 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket water pump impeller is designed for selected Mercury and Mariner 2-stroke outboards rated from 3.9 to 9.8 HP that use the 0.456-inch shaft version. The company application range includes 3.9, 4, 4.5, 6, 7.5, and 9.8 HP models. Verify the shaft size and the complete engine application before ordering, because the related 0.438-inch impeller version is different.
This impeller is listed for applications using Mercury OEM references 47-89981, 47-89981T2, 47-65957, and 47-39074. The corresponding aftermarket reference is 18-3039. These numbers are application references only; this listing is not an OEM Mercury component.
- Single aftermarket water pump impeller.
- For selected Mercury and Mariner 2-stroke outboards.
- 0.456-inch internal shaft diameter version.
- Impeller only; gasket, key, housing, wear plate, and complete repair-kit components are not included.
Part Number Matrix
Use the following references to compare the impeller with your original part and service documentation.
| Brand or Source | Part Number | Reference Type |
|---|---|---|
| Mercury | 47-89981, 47-89981T2, 47-65957, 47-39074 | OEM application references |
| Sierra | 18-3039 | Aftermarket reference |
| GLM | 12270 | Catalog reference; verify exact product scope before substituting a kit |
Engine & Model Compatibility
The compatibility information below is a consolidated application guide. Mercury and Mariner fitment can vary by model designation, serial number, production year, and water-pump configuration. Match all conditions and confirm that your original impeller has the 0.456-inch internal diameter.
| Brand | Rated HP | Stroke | Shaft Version | Known Application Scope | OEM Reference |
|---|---|---|---|---|---|
| Mercury / Mariner | 3.9 | 2-Stroke | 0.456 in | Selected models; verify model and serial number | 47-89981 family |
| Mercury / Mariner | 4 | 2-Stroke | 0.456 in | Selected models; some catalog applications are listed for 1975–1985 | 47-89981 family |
| Mercury / Mariner | 4.5 | 2-Stroke | 0.456 in | Selected models; some catalog applications are listed for 1975–1985 | 47-89981 family |
| Mercury / Mariner | 6 | 2-Stroke | 0.456 in | Selected models; verify model and serial number | 47-89981 family |
| Mercury / Mariner | 7.5 | 2-Stroke | 0.456 in | Selected models; some catalog applications are listed for 1975–1985 | 47-89981 family |
| Mercury / Mariner | 9.8 | 2-Stroke | 0.456 in | Selected models; some catalog applications are listed for 1975–1985 | 47-89981 family |
Technical Specs
- Product Type
- Water pump impeller
- Application
- Selected Mercury and Mariner 2-stroke outboards
- Rated Horsepower Range
- 3.9, 4, 4.5, 6, 7.5, and 9.8 HP applications
- Internal Shaft Diameter
- 0.456 inch
- External Diameter
- 1.250 inches reference dimension
- Aftermarket Reference
- 18-3039
- OEM References
- 47-89981, 47-89981T2, 47-65957, and 47-39074
- Included Quantity
- 1 impeller
What’s in the Box
- 1 x aftermarket water pump impeller
Gaskets, keys, pump housings, wear plates, and other water-pump components are sold separately unless specifically included with your order.
Installation Notes
- Confirm the engine model, serial number, stroke, and 0.456-inch impeller shaft specification before disassembly.
- Disconnect the battery and follow the service manual for safe lower-unit removal.
- Remove the lower unit and expose the water-pump housing according to the manufacturer’s procedure.
- Remove the housing and old impeller, noting the original installation direction and any drive-pin arrangement.
- Inspect the pump housing, wear plate, drive pin, seals, and related components for wear or damage.
- Clean the pump cavity and confirm that the replacement impeller matches the original 0.456-inch internal diameter version.
- Install the impeller using a suitable water-pump lubricant and the correct orientation for the engine’s rotation.
- Reassemble the water-pump housing and lower unit using the manufacturer’s specified gaskets, torque values, and alignment procedure.
- Refill the gearcase with the correct lubricant if required by the service procedure.
- Run the engine only in an appropriate test tank or in the water, and verify a steady cooling-water telltale stream before normal operation.
Troubleshooting & FAQ
How do I know if this impeller fits my Mercury or Mariner outboard?
Confirm that your engine is a listed 2-stroke application in the 3.9, 4, 4.5, 6, 7.5, or 9.8 HP range and that the original impeller uses the 0.456-inch internal shaft diameter. Also check the exact model and serial number because horsepower alone does not establish fitment.
Is this the same as the 0.438-inch impeller?
No. The 0.456-inch and 0.438-inch versions are different applications. Measure or identify the original part and confirm the OEM reference before ordering.
What are the signs of a failing water-pump impeller?
Common signs include overheating, a weak or missing telltale stream, reduced cooling-water flow, or visible cracking, brittleness, distortion, or missing vanes when the impeller is inspected.
How often should the impeller be replaced?
Inspect the impeller during scheduled maintenance and replace it when it shows wear, damage, hardening, deformation, or loss of vanes. Follow the maintenance interval recommended for your specific engine and operating conditions.
Does this listing include a gasket or key?
No. This listing is for one impeller only. Gaskets, keys, housings, wear plates, and complete water-pump repair kits are not included.
Can I run the outboard without water?
No. Never operate the engine without an adequate water supply. Running a water-pump impeller dry can quickly damage the impeller and may cause engine overheating.
Is this an OEM Mercury part?
No. This is an aftermarket replacement impeller referenced to the listed Mercury OEM application numbers.
Safety & Important Info
- Verify the complete engine model, serial number, stroke, and impeller dimensions before purchase and installation.
- Do not substitute the 0.438-inch version for the 0.456-inch version.
- Do not operate the outboard without a proper water supply.
- Use the manufacturer’s service manual for disassembly, torque, lubrication, and reassembly instructions.
- Professional installation is recommended if you are not experienced with outboard lower-unit or water-pump service.
About Sea Sierra
- Marine Replacement Parts — Practical aftermarket components for routine outboard maintenance and repair.
- Application-Focused Listings — Product references and fitment details are provided to help you compare the part with your original equipment.
- Support When You Need It — Contact support with your engine model and serial information if you need help confirming an application.
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