Water Pump Impeller Repair Kit – Fits Mercury Marine 4–9.8 HP (Replaces 47-89981Q1, 47-89981T1, 47-89981T2)
Water Pump Impeller Repair Kit – Fits Mercury Marine 4–9.8 HP (Replaces 47-89981Q1, 47-89981T1, 47-89981T2) 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.
U.S. orders usually arrive within 6–15 days, depending on stock location and destination.
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Water Pump Impeller Repair Kit – Fits Mercury Marine 4–9.8 HP (Repl...
Water Pump Impeller Repair Kit – Fits Mercury Marine 4–9.8 HP (Replaces 47-89981Q1, 47-89981T1, 47-89981T2) is backordered and will ship as soon as it is back in stock.
Product Details
This Water Pump Impeller Repair Kit is designed for Mercury and Mariner 4, 4.5, 6, 7.5, and 9.8 HP 2-stroke outboard motors manufactured between 1975 and 1986. The kit provides all the necessary components for a complete overhaul of the lower unit water pump to restore cooling performance.
It serves as a direct replacement for Mercury part numbers 47-89981Q1, 47-89981T1, and 47-89981T2, as well as Sierra 18-3239, GLM 12270, and Soxa Marine 18KM001.
- Installs in the lower unit housing.
- Features a durable neoprene impeller with a brass hub for reliable performance.
- Includes a marine-grade SS316 stainless steel wear plate and essential seals.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket brands.
| Brand | Part Number |
|---|---|
| Mercury | 47-89981Q1 |
| Mercury | 47-89981T1 |
| Mercury | 47-89981T2 |
| Sierra | 18-3239 |
| GLM | 12270 |
| Soxa Marine | 18KM001 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Mercury/Mariner Outboards, it is critical to verify the serial number (S/N) range to ensure correct fitment. This kit is not compatible with all engines in the listed horsepower range.
| Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Mercury 4 HP | 4 | 2-Stroke | 1975–1986 | 47-89981Q1 | For S/N 5595532 & Up U.S. |
| Mercury 4.5 HP | 4.5 | 2-Stroke | 1975–1986 | 47-89981Q1 | For S/N 5595532 & Up 1 cylinder |
| Mercury 6 HP | 6 | 2-Stroke | 1975–1986 | 47-89981Q1 | For S/N 1916139 through 2529894 |
| Mercury 7.5 HP | 7.5 | 2-Stroke | 1975–1986 | 47-89981Q1 | Model 75, S/N 5206550 & Up |
| Mercury 9.8 HP | 9.8 | 2-Stroke | 1975–1986 | 47-89981Q1 | Model Merc 110, S/N 5206550 & Up |
Technical Specs
- Product Type
- Water Pump Impeller Kit
- Installation
- Lower Unit
- Material
- Neoprene Impeller with Brass Hub, Marine Grade SS316 Wear Plate
- Impeller Blades
- 6
- Impeller Height
- 14.4 mm (0.57 inches)
- Overall Diameter
- 32.0 mm (1.26 inches)
- Shaft Diameter
- 11.0 mm (0.456 inches)
- Weight
- 11 g (0.45 oz)
- Housing Material
- Marine Grade SS316
- Warranty
- 1 Year
What’s in the Box
- 1 x Impeller (47-89981/18-3039)
- 1 x Wear Plate (46895)
- 1 x Key, Woodruff Impeller
- 1 x Sleeve, Guide Water Inlet Tube
- 1 x Seal (700-85651)
- 2 x O-ring (700-81230, 700-81090)
Installation Notes
- Disconnect the spark plug wires and shift the engine into neutral.
- Remove the bolts securing the lower unit (gearcase) and carefully drop it down.
- Unbolt and remove the water pump housing cover to access the old impeller.
- Take note of the old impeller's blade orientation before removing it. Remove the Woodruff key from the driveshaft.
- Clean the housing interior and inspect the wear plate and housing for scoring or cracks. Replace if damaged.
- Install the new Woodruff key, then slide the new impeller onto the driveshaft while twisting it in the direction of engine rotation to properly seat the blades.
- Install the new wear plate and O-rings/seals. Re-install the housing.
- Lightly grease the driveshaft splines and reinstall the lower unit, ensuring the water tube and shift shaft align correctly.
Troubleshooting & FAQ
Will this kit fit my 5 HP Mercury outboard?
No. Multiple sources confirm this impeller kit will NOT fit 5 HP Mercury or Mariner engines. Please verify your engine's horsepower and serial number against the compatibility chart.
Is the impeller shaft size important?
Yes, it is critical. This impeller is designed for a driveshaft diameter of 11.0 mm (0.456 inches). Using an incorrect size will result in pump failure and potential engine damage.
Why is my engine's serial number so important?
Manufacturers often make mid-year changes to engine components. This kit is only verified to fit the specific serial number ranges listed in the compatibility table. Always check your engine's S/N before ordering.
When should I replace my water pump impeller?
For preventative maintenance, it is recommended to replace the impeller every 1-2 years or every 100-200 hours of operation, especially if used frequently in saltwater or silty conditions.
What are the signs of a failing water pump impeller?
Common symptoms include a weak or nonexistent water stream from the "telltale" outlet, engine overheating alerts, or a physically brittle, cracked, or deformed impeller upon inspection.
Is this an OEM part or an aftermarket one?
This listing is an aftermarket replacement (not OEM). It is built to OEM-level specifications with comparable materials and manufactured in an ISO 9002 facility, with batch inspections for quality and consistency.
How fast do you ship and what is the cost?
We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free, and any available expedited options will appear at checkout.
What is the warranty and return policy?
This part is 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 for unused items in their 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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