Water Pump Impeller Kit – Fits Mercury/Mariner 2-Stroke 3.9HP-9.8HP (Replaces 47-89981Q1, 47-89981T1)
Water Pump Impeller Kit – Fits Mercury/Mariner 2-Stroke 3.9HP-9.8HP (Replaces 47-89981Q1, 47-89981T1) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
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Water Pump Impeller Kit – Fits Mercury/Mariner 2-Stroke 3.9HP-9.8HP...
Water Pump Impeller Kit – Fits Mercury/Mariner 2-Stroke 3.9HP-9.8HP (Replaces 47-89981Q1, 47-89981T1) is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket Water Pump Impeller Kit – Fits Mercury/Mariner 2-Stroke 3.9HP-9.8HP (Replaces 47-89981Q1, 47-89981T1) is designed for a range of Mercury and Mariner 2-stroke outboard engines from the 1970s and 1980s, including 3.9HP, 4HP, 4.5HP, 6HP, 7.5HP, and 9.8HP models. It serves as a complete assembly for water pump repair and rebuilds, ensuring proper engine cooling.
The kit provides a direct replacement for Mercury part numbers 47-89981Q1, 47-89981T1, and 89981T2, and interchanges with Sierra 18-3039, GLM 12270, and Mallory 9-45035.
- Engineered for direct-fit installation.
- Features a 0.456" inner diameter to fit the driveshaft.
- Includes the essential impeller for a complete water pump service.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 47-89981Q1 |
| Mercury | 47-89981T1 |
| Mercury | 89981T2 |
| Sierra | 18-3039 |
| GLM | 12270 |
| Mallory | 9-45035 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Mercury/Mariner outboards, this kit fits various single-cylinder and other models primarily from the 1970s-1980s. Verify your engine's serial number range where applicable.
| Brand | Model | Rated HP | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Mercury | Outboard | 3.9 | 2-Stroke | 47-89981Q1 | Single cylinder |
| Mercury | Outboard | 4 | 2-Stroke | 47-89981Q1 | Serial (1 cyl.) 2498136-4107219 |
| Mercury | Outboard | 4 | 2-Stroke | 47-89981Q1 | Serial (made in USA) 5595532 & UP |
| Mercury | Outboard | 4.5 | 2-Stroke | 47-89981Q1 | Serial 4107220-5595531 |
| Mercury | Outboard | 6 | 2-Stroke | 47-89981Q1 | |
| Mercury | Outboard | 7.5 | 2-Stroke | 47-89981Q1 | |
| Mercury | Outboard | 9.8 | 2-Stroke | 47-89981Q1 |
Technical Specs
- Product Type
- Water Pump Impeller Kit
- Installation
- Direct replacement
- Connection
- 0.456" ID (Driveshaft)
- Housing Color
- Black
- Warranty
- 90 Days (Aftermarket)
- Other Technical Attributes
- Water pump repair/rebuild kit assembly
What’s in the Box
- 1 x Water Pump Impeller (47-89981Q1/47-89981T1/89981T2)
Installation Notes
- Disconnect the battery and shift the outboard into neutral.
- Remove the lower unit (gearcase) by unbolting it from the engine's driveshaft housing.
- Locate and unbolt the water pump housing cover.
- Take note of the old impeller's vane orientation before removing it from the driveshaft.
- Clean any debris or corrosion from the housing interior and wear plate.
- Lightly grease the new impeller and install it onto the driveshaft, turning the shaft in the direction of engine rotation to bend the vanes correctly.
- Reassemble the water pump housing, ensuring all seals and gaskets are properly seated.
- Reattach the lower unit to the engine and test operation in a safe water environment.
Troubleshooting & FAQ
How do I know if this impeller kit fits my engine?
First, check the Engine & Model Compatibility table on this page. If your model is listed, verify the OEM part number and any serial number ranges noted. Visually comparing the images to your old part is the final step to confirm a match.
What are the signs of a failing water pump impeller?
Common symptoms include the engine overheating at idle or low speeds, a weak or non-existent "telltale" water stream, and, in severe cases, an engine alarm. The rubber vanes can become brittle, cracked, or worn down over time.
How often should I replace my outboard's impeller?
As a general maintenance rule, it is recommended to inspect and/or replace the water pump impeller every 1-2 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.
My engine still overheats after replacing the impeller. What else could be wrong?
If overheating persists, check for other blockages in the cooling system, such as clogged water intake screens, a faulty thermostat, or obstructions within the engine's cooling passages. Also, ensure the impeller was installed with the vanes bent in the correct rotational direction.
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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