Water Pump Impeller Kit for Mercury Marine 20 HP 2-Stroke Outboards – Replaces 47-56780, 47-65958, 47-89982 and 47-89982B
Water Pump Impeller Kit for Mercury Marine 20 HP 2-Stroke Outboards – Replaces 47-56780, 47-65958, 47-89982 and 47-89982B is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
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Water Pump Impeller Kit for Mercury Marine 20 HP 2-Stroke Outboards...
Water Pump Impeller Kit for Mercury Marine 20 HP 2-Stroke Outboards – Replaces 47-56780, 47-65958, 47-89982 and 47-89982B is backordered and will ship as soon as it is back in stock.
Product Details
This water pump impeller kit is designed for Mercury Marine 20 HP 2-Stroke outboard engines listed for model years 1970–1985. The impeller circulates cooling water through the engine to help maintain proper operating temperature and reduce the risk of overheating.
This aftermarket replacement kit is listed as an interchange for Mercury OEM numbers 47-56780, 47-65958, 47-89982, and 47-89982B. Related aftermarket reference numbers include GLM 89820, Mallory 9-45311, and Sierra 18-3052.
- Installs in the lower gearcase water pump assembly.
- Impeller is made from flexible neoprene with a brass hub.
- Kit includes a replacement drive key for installation.
- Designed to restore water flow through the outboard cooling system when the original impeller is worn or damaged.
Part Number Matrix
Use the following references to compare the listed OEM and aftermarket numbers with the part removed from your engine.
| Brand | Part Number |
|---|---|
| Mercury | 47-56780 |
| Mercury | 47-65958 |
| Mercury | 47-89982 |
| Mercury | 47-89982B |
| GLM | 89820 |
| Mallory | 9-45311 |
| Sierra | 18-3052 |
Engine & Model Compatibility
Confirm the model designation, horsepower, stroke, model year, and original impeller number before ordering.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 200 | 20 | 2-Stroke | 1970–1985 | 47-89982 | Also listed as 47-56780, 47-65958, and 47-89982B |
Technical Specifications
- Product Type
- Water pump impeller kit
- Installation Location
- Lower gearcase water pump assembly
- Drive Connection
- Driveshaft
- Impeller Material
- Neoprene with brass hub
- Impeller Color
- Black and brass
- Fitment Type
- Aftermarket replacement
- Included Installation Component
- Drive key
What’s in the Box
- 1 x Water pump impeller
- 1 x Drive key
This listing does not specify a face plate, plate gasket, slinger, or O-ring as included components. Inspect the existing water pump assembly and obtain any additional service parts required for your particular engine.
Installation Notes
- Disconnect the battery and place the outboard in neutral.
- Drain the gearcase oil from the lower unit.
- Unbolt and carefully lower the gearcase from the outboard’s driveshaft housing.
- Remove the fasteners securing the water pump housing to the gearcase.
- Remove the pump housing and old impeller from the driveshaft, noting the original impeller-vane orientation.
- Clean the driveshaft, pump housing, and mating surfaces. Remove debris and old gasket residue.
- Install the supplied drive key, then slide the new impeller onto the driveshaft.
- Apply a light coat of marine grease or an appropriate installation lubricant to the housing interior. Install the housing over the impeller while rotating the driveshaft clockwise so the vanes seat correctly.
- Reinstall the water pump fasteners and lower unit. Refill the gearcase with the correct fresh lubricant before operating the engine.
- Start the engine only in a suitable water supply and verify that cooling-water flow is present.
Troubleshooting & FAQ
How do I know if my water pump impeller is failing?
Common signs include an overheating alarm, weak or absent water flow from the tell-tale outlet, or an unusually high temperature reading. Inspect the impeller for hardened, cracked, torn, or permanently distorted vanes during routine service.
How often should the impeller be replaced?
Many outboard service schedules recommend replacement every 1 to 2 years or every 100–200 operating hours, whichever comes first. More frequent service may be appropriate when operating in sandy, silty, or saltwater conditions. Follow the service schedule for your specific engine.
Why are the impeller vanes bent?
The flexible neoprene vanes bend inside the offset water pump housing. As the driveshaft rotates, the vanes create suction at the pump inlet and pressure that moves cooling water through the engine.
Is this a difficult part to install?
Installation requires removal and refitting of the gearcase and careful assembly of the water pump. Moderate mechanical skill and the correct tools are required. If you are not familiar with outboard lower-unit service, professional installation is recommended.
Is this an OEM part?
No. This is an aftermarket replacement impeller kit listed for the stated Mercury applications and reference numbers.
What should I verify before ordering?
Compare the original impeller, drive key, OEM reference number, engine model, horsepower, stroke, and model year. Model and year ranges can vary by serial-number or production configuration, so do not rely on horsepower alone.
Shipping speed and cost
Standard and expedited shipping options, availability, and delivery estimates are shown at checkout based on the destination.
Warranty and returns
Warranty coverage and return eligibility are governed by the applicable order and store policies. Contact support with your order details if you need assistance.
Safety & Important Information
- Verify the engine model, year, stroke, serial-number range where applicable, and original part number before installation.
- Do not operate the outboard without an adequate water supply.
- Stop the engine immediately if cooling-water flow is weak or absent, or if an overheating warning occurs.
- This is an aftermarket replacement, not a Mercury OEM component.
- Professional installation is recommended when lower-unit service experience or the required tools are unavailable.
About Sea Sierra
- Pro-Grade Standards — We supply marine replacement parts selected for dependable service in real-world conditions.
- Global Fulfillment — Available delivery options and estimated transit times are presented at checkout.
- Manufacturer-Direct Value — Competitive pricing focused on practical replacement solutions.
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