Water Pump Impeller – Fits Mercury Marine 20 HP (Replaces 47-89982, 47-56780, 47-65958, 47-89982B)
Water Pump Impeller – Fits Mercury Marine 20 HP (Replaces 47-89982, 47-56780, 47-65958, 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 – Fits Mercury Marine 20 HP (Replaces 47-89982,...
Water Pump Impeller – Fits Mercury Marine 20 HP (Replaces 47-89982, 47-56780, 47-65958, 47-89982B) is backordered and will ship as soon as it is back in stock.
Product Details
This Water Pump Impeller – Fits Mercury Marine 20 HP (Replaces 47-89982) is an essential component for maintaining engine cooling in Mercury Marine 20 HP 2-Stroke outboard engines from model years 1970–1985. It ensures reliable water circulation to prevent overheating and maintain optimal performance.
This part provides a direct interchange for Mercury OEM numbers 47-56780, 47-65958, 47-89982, and 47-89982B, and is also equivalent to aftermarket parts from GLM (89820), Mallory (9-45311), and Sierra (18-3052).
- Installs in the lower gearcase to drive the engine's cooling system.
- Constructed from durable neoprene with a brass hub for corrosion resistance.
- A drive key is included in most kits for a complete replacement.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket brands.
| 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 your engine model/year in the table below.
| 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, 47-89982B |
Technical Specs
- Product Type
- Water Pump Impeller
- Installation
- Lower Gearcase
- Connection
- Driveshaft
- Housing Material
- Neoprene with Brass Hub
- Housing Color
- Black/Brass
- Fitting Type
- Direct Fit
- Other Technical Attributes
- Key included with most replacement kits
What’s in the Box
Package contents vary by manufacturer but typically include:
- 1 x Water Pump Impeller (47-89982)
- 1 x Drive Key
Some kits may additionally include:
- 1 x Face Plate
- 1 x Plate Gasket
- 1 x Slinger
- 1 x O-Ring
Installation Notes
- Disconnect the battery and shift the outboard into neutral.
- Drain the gearcase oil from the lower unit.
- Unbolt and carefully lower the gearcase from the outboard's driveshaft housing.
- Remove the bolts securing the water pump housing to the gearcase.
- Slide the old pump housing and impeller off the driveshaft. Note the orientation of the old impeller vanes.
- Clean the driveshaft and housing interior, removing any debris or gasket residue.
- Install the new drive key and slide the new impeller onto the driveshaft. Rotate the driveshaft clockwise to bend the vanes correctly.
- Apply a light coat of marine grease or soap to the inside of the new housing and install it over the impeller.
- Reinstall the water pump bolts, lower unit, and refill the gearcase with fresh oil before starting the engine.
Troubleshooting & FAQ
How do I know if my water pump impeller is failing?
Common signs of a worn or damaged impeller include an engine overheating alarm, a weak or non-existent water stream from the "tell-tale" outlet, or an unusually high reading on your temperature gauge. Visual inspection during routine maintenance is the best way to catch wear before it causes a failure.
What is the recommended replacement interval for an impeller?
For most outboard engines, it is recommended to replace the water pump impeller every 1 to 2 years or every 100-200 hours of operation, whichever comes first. This interval can be shorter if you frequently operate in sandy, silty, or saltwater conditions.
Why are the impeller vanes bent?
The flexible neoprene vanes are designed to bend inside the offset water pump housing. As the driveshaft spins, the vanes flex and straighten, creating suction to draw water in and pressure to push it up into the engine's cooling passages.
Is this a difficult part to install?
Installation requires lowering the gearcase, which can be done by individuals with moderate mechanical skill and the correct tools. However, due to the importance of correct assembly for engine safety, professional installation is recommended to prevent cooling system failures.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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