Water Pump Impeller – Fits Mercury 3.9-9.8 HP Outboards (Replaces Mercury 47-89981)
Water Pump Impeller – Fits Mercury 3.9-9.8 HP Outboards (Replaces Mercury 47-89981) is backordered and will ship as soon as it is back in stock.
Worry-free returns
Worry-free returns
Shop with confidence. If you’re not completely satisfied, eligible items may be returned within the return window, provided they are unused and in original packaging.
If the return is due to our error or a defective item, we’ll make it right.
Please contact us before returning any item.
Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
U.S. orders usually arrive within 6–15 days, depending on stock location and destination.
International delivery times may vary due to customs processing.
Tracking information will be provided once your order ships.
Water Pump Impeller – Fits Mercury 3.9-9.8 HP Outboards (Replaces M...
Water Pump Impeller – Fits Mercury 3.9-9.8 HP Outboards (Replaces Mercury 47-89981) is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket Water Pump Impeller – Fits Mercury 3.9-9.8 HP Outboards (Replaces 47-89981) is designed for specific Mercury 1-cylinder 4 HP (1982–1985), 4.5 HP (1980–1985), 7.5 HP (1979–1986), and 9.8 HP (1979–1985) 2-Stroke outboards that use a 0.456" diameter driveshaft. It is crucial to verify your driveshaft size, as this part will not fit models with smaller shafts or any 5 HP Mercury/Mariner engines.
It serves as a direct replacement for Mercury part numbers 47-89981, 47-89981Q1, 47-89981T1, and 47-89981T2, and interchanges with equivalents from Sierra, GLM, Mallory, and SEI Marine.
- Made from durable neoprene rubber with a brass hub for corrosion resistance.
- Engineered for the larger 0.456" outer diameter driveshaft version.
- Includes one water pump impeller as pictured.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 47-89981, 47-89981Q1, 47-89981T1, 47-89981T2 |
| Sierra | 18-3039 |
| GLM | 12270, 89810 |
| Mallory | 9-45305 |
| SEI Marine | 96-260-03B |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
Fitment for these Mercury models is highly dependent on the serial number and driveshaft diameter. This impeller is for models with a 0.456" driveshaft. Please verify your specific application before ordering.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 1-cylinder | 4 | 2-Stroke | 1982–1985 | 47-89981 | S/N 2498136-4107219 |
| Mercury | - | 4.5 | 2-Stroke | 1980–1985 | 47-89981 | S/N 4107220 and up |
| Mercury | - | 7.5 | 2-Stroke | 1979–1986 | 47-89981 | S/N 4131610 and up |
| Mercury | (Model 110) | 9.8 | 2-Stroke | 1979–1985 | 47-89981 | S/N 1865779 and up |
Technical Specs
- Product Type
- Water Pump Impeller
- Material
- Neoprene rubber with brass hub
- Number of Blades
- 6
- Impeller Height
- 11.6 mm (0.456 inch)
- Overall Diameter
- 32 mm (1.260 inch)
- Shaft Diameter
- 14.4 mm (0.567 inch)
- Driveshaft Size
- 0.456 inch outer diameter
- Weight
- 10 g (0.022 lb)
- Warranty
- 1 Year (aftermarket)
What’s in the Box
- 1 x Water Pump Impeller (47-89981)
Installation Notes
- Disconnect the battery and remove the engine cover.
- Drain the lower unit gear lube completely.
- Remove the bolts securing the lower unit (gearcase) to the engine's midsection.
- Carefully separate and lower the gearcase from the driveshaft housing.
- Locate and unbolt the water pump housing on top of the gearcase to expose the old impeller.
- Remove the old impeller, noting the original orientation of the blades.
- Clean the housing interior and inspect it for wear or damage.
- Install the new impeller, using a twisting motion in the direction of engine rotation to bend the blades correctly.
- Apply a light coat of marine grease or soapy water to the new impeller and housing.
- Reassemble the water pump, gearcase, and all components in reverse order, ensuring proper alignment and torque on all bolts.
- Refill the gearcase with the correct type and amount of lube.
- Test the engine in water to confirm a strong, steady stream from the telltale outlet.
Troubleshooting & FAQ
How do I know if this impeller fits my Mercury outboard?
This impeller is specifically for older Mercury 3.9 HP to 9.8 HP models that use a 0.456-inch diameter driveshaft. You must verify this dimension. It will not fit models with a smaller driveshaft or any 5 HP engines. Check the compatibility table and your engine's serial number range for a precise match.
What are the signs of a failing water pump impeller?
Common signs include the engine overheating at idle or low speeds, a weak or non-existent stream of water from the "telltale" outlet, and a dry, cracked, or brittle appearance of the old impeller upon inspection.
How often should the water pump impeller be replaced?
As a general maintenance guideline, it is recommended to inspect the impeller annually and replace it every 1–2 years or every 100–200 hours of use, whichever comes first. This interval can be shorter if you frequently operate in sandy or silty water.
The new impeller looks slightly different from my original. Can I still use it?
No. While aftermarket parts may have minor cosmetic differences, the critical dimensions (height, diameter, shaft size, number of blades) must match exactly. If there are any discrepancies, do not install the part. This impeller has 6 blades and is 11.6 mm tall.
Is a gasket included with this part?
This listing is for the impeller only, as shown in the "What’s in the Box" section. Gaskets, housing, and other components of a full water pump repair kit are sold separately.
What is the main cause of premature impeller failure?
The most common cause is running the outboard "dry" (out of the water) for even a few seconds. Water acts as both a coolant and lubricant for the impeller. Without it, the rubber quickly overheats and can be permanently damaged.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). It is built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility and batch-inspected for consistency.
Shipping speed & cost
We ship worldwide quickly—typical transit is 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 and specifications against 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 quality control.
Payment & Security
Payment methods
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
