Aftermarket 2-Stroke Water Pump Impeller for Mercury Mariner 3.5, 3.6, 4, 4.5, 7.5 & 9.8 HP – 0.438 in Shaft – Replaces OEM 47-68988 / 47-89980
Aftermarket 2-Stroke Water Pump Impeller for Mercury Mariner 3.5, 3.6, 4, 4.5, 7.5 & 9.8 HP – 0.438 in Shaft – Replaces OEM 47-68988 / 47-89980 is backordered and will ship as soon as it is back in stock.
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Aftermarket 2-Stroke Water Pump Impeller for Mercury Mariner 3.5, 3...
Aftermarket 2-Stroke Water Pump Impeller for Mercury Mariner 3.5, 3.6, 4, 4.5, 7.5 & 9.8 HP – 0.438 in Shaft – Replaces OEM 47-68988 / 47-89980 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket 2-stroke water pump impeller is designed for selected Mercury and Mariner outboards rated from 3.5 HP through 9.8 HP. It has a 0.438-inch shaft opening and is intended to restore water circulation through the outboard cooling system when the original impeller is worn or damaged.
The impeller is listed as a replacement for Mercury OEM references 47-68988, 47-89980, and 47-89980T1. Sierra reference 18-3054 is also listed for the same 0.438-inch impeller application.
- Aftermarket replacement water pump impeller.
- For 2-stroke Mercury and Mariner outboards.
- 0.438-inch shaft opening.
- Installs in the lower-unit water pump assembly.
Part Number Matrix
Use the following references when comparing your existing impeller and engine parts information.
| Reference Type | Part Number | Application Note |
|---|---|---|
| Mercury OEM | 47-68988 | Replacement reference for the 0.438-inch impeller application. |
| Mercury OEM | 47-89980 | Replacement reference for the 0.438-inch impeller application. |
| Mercury OEM | 47-89980T1 | Reference associated with the 0.438-inch impeller application. |
| Sierra aftermarket | 18-3054 | Listed for Mercury Marine 47-68988 and 47-89980. |
Engine & Model Compatibility
The company fitment record specifies 2-stroke Mercury Mariner applications with a 0.438-inch shaft opening. Confirm the exact model and serial-number range before ordering; horsepower alone does not establish fitment.
| Brand | Rated HP / Model | Stroke | Shaft Opening | Serial or Model Note |
|---|---|---|---|---|
| Mercury Mariner | 3.5 HP | 2-stroke | 0.438 in | Verify the exact engine model and serial number. |
| Mercury Mariner | 3.6 HP | 2-stroke | 0.438 in | Verify the exact engine model and serial number. |
| Mercury Mariner | 4 HP | 2-stroke | 0.438 in | Verify the exact engine model and serial number. |
| Mercury Mariner | 4.5 HP | 2-stroke | 0.438 in | Verify the exact engine model and serial number. |
| Mercury Mariner | 7.5 HP | 2-stroke | 0.438 in | Verify the exact engine model and serial number. |
| Mercury Mariner | 9.8 HP | 2-stroke | 0.438 in | Verify the exact engine model and serial number. |
Important: This listing is for the 2-stroke, 0.438-inch application. Do not use it for a 4-stroke engine or for an impeller with a different shaft opening unless your engine parts documentation specifically confirms compatibility.
Technical Specifications
- Product Type
- Water pump impeller
- Application
- Mercury Mariner 2-stroke outboards
- Horsepower Range
- 3.5, 3.6, 4, 4.5, 7.5 and 9.8 HP applications
- Shaft Opening
- 0.438 in
- Replacement References
- Mercury 47-68988, 47-89980 and 47-89980T1; Sierra 18-3054
- Product Configuration
- Single replacement impeller; no housing, wear plate, gasket or other water-pump components included unless separately stated.
What’s in the Box
- 1 x Aftermarket 2-stroke water pump impeller
Installation Notes
- Disconnect the battery and spark plug leads before servicing the outboard.
- Place the engine in neutral and remove the lower unit according to the manufacturer’s service procedure.
- Remove the water pump housing and take out the old impeller.
- Inspect the pump housing, wear plate, key or drive pin, seals and related components for wear or damage. Replace damaged components before reassembly.
- Clean debris from the pump cavity and note the original impeller blade orientation.
- Install the replacement impeller on the driveshaft, aligning it with the original key or drive-pin arrangement. Use an appropriate marine lubricant during installation if specified by the service manual.
- Reinstall the pump housing and lower unit, following the engine manufacturer’s alignment and torque procedures.
- Test the engine using an appropriate water supply and confirm a steady cooling-water tell-tale stream before normal operation.
Troubleshooting & FAQ
How do I confirm that this impeller fits my engine?
Confirm all of the following: Mercury or Mariner branding, 2-stroke configuration, the listed horsepower/model, a 0.438-inch shaft opening, and the correct engine serial-number range. Compare the old impeller and water-pump assembly before ordering.
Is this impeller for 2-stroke or 4-stroke engines?
The company fitment record specifies 2-stroke Mercury Mariner applications only. The listing should not be treated as a 4-stroke fitment.
Which OEM references does this impeller replace?
The listed Mercury OEM references are 47-68988, 47-89980 and 47-89980T1. Sierra 18-3054 is a corresponding aftermarket reference listed for the 0.438-inch application.
What are the signs of a worn water pump impeller?
Possible signs include overheating, a weak or absent tell-tale stream, reduced cooling-water flow, or visible cracking and deformation when the impeller is removed. Inspect the complete water-pump assembly before returning the engine to service.
Does the package include a key, housing or gasket?
No. This listing is for one replacement impeller only. A housing, wear plate, gasket, key or drive pin is not included unless specifically stated for your order.
Is this an OEM Mercury part?
No. This is an aftermarket replacement impeller intended for the stated applications and reference numbers.
Safety & Important Information
- Verify the engine model, serial number, stroke type and shaft opening before ordering.
- Do not rely on horsepower alone to determine compatibility.
- Inspect the pump housing, wear plate, key or drive pin and seals during installation.
- Follow the outboard manufacturer’s service manual for removal, installation and torque procedures.
- Professional installation is recommended if you are not familiar with outboard lower-unit service.
About Sea Sierra
- Marine Replacement Parts — Practical aftermarket components for routine outboard service and repair.
- Application-Focused Listings — Product references and fitment details are provided to help you compare your original part.
- Support for Correct Selection — Always compare the engine model, serial number and original component before ordering.
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