Water Pump Impeller Repair Kit for Mercury and Mariner 4–9.8 HP 2-Stroke Outboards – Replaces 47-89981Q1, 47-89981T1 and 47-89981T2
Water Pump Impeller Repair Kit for Mercury and Mariner 4–9.8 HP 2-Stroke Outboards – Replaces 47-89981Q1, 47-89981T1 and 47-89981T2 is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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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.
International delivery times may vary due to customs processing.
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Water Pump Impeller Repair Kit for Mercury and Mariner 4–9.8 HP 2-S...
Water Pump Impeller Repair Kit for Mercury and Mariner 4–9.8 HP 2-Stroke Outboards – Replaces 47-89981Q1, 47-89981T1 and 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 the components needed to service the lower-unit water pump and help restore proper cooling-water flow.
It replaces or cross-references Mercury part numbers 47-89981Q1, 47-89981T1, and 47-89981T2, as well as Sierra 18-3239, GLM 12270, and Soxa Marine 18KM001. Confirm the engine model, year, and serial-number range before ordering.
- Installs in the lower-unit water-pump assembly.
- Includes a durable neoprene impeller with a brass hub.
- Includes a marine-grade SS316 wear plate and associated seals and O-rings.
Part Number Matrix
Use this matrix to compare the listed OEM and aftermarket references. Part-number appearance alone does not replace model and serial-number verification.
| 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, horsepower, stroke, and serial number against the table below before purchase. Mercury and Mariner outboards can have mid-year production changes, so the serial-number range is important for fitment.
| Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Mercury 4 HP | 4 | 2-Stroke | 1975–1986 | 47-89981Q1 | For S/N 5595532 and up, U.S. |
| Mercury 4.5 HP | 4.5 | 2-Stroke | 1975–1986 | 47-89981Q1 | For S/N 5595532 and up; 1-cylinder model |
| 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 and up |
| Mercury 9.8 HP | 9.8 | 2-Stroke | 1975–1986 | 47-89981Q1 | Mercury 110 model; S/N 5206550 and up |
Technical Specs
- Product Type
- Water Pump Impeller Repair Kit
- Installation
- Lower unit
- Impeller Material
- Neoprene with brass hub
- Wear Plate Material
- Marine-grade SS316 stainless steel
- 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)
- Warranty
- 1 year
What’s in the Box
- 1 x Impeller, equivalent to 47-89981 and Sierra 18-3239
- 1 x Wear Plate, 46895
- 1 x Woodruff impeller key
- 1 x Guide sleeve for the water-inlet tube
- 1 x Seal, 700-85651
- 2 x O-rings, 700-81230 and 700-81090
Installation Notes
- Disconnect the spark-plug wires and shift the engine into neutral.
- Remove the bolts securing the lower unit or gearcase, then carefully lower the unit.
- Remove the water-pump housing cover to access the old impeller.
- Note the old impeller-blade orientation before removal. Remove the Woodruff key from the driveshaft.
- Clean the housing interior and inspect the wear plate and housing for scoring, cracks, or other damage. Replace damaged components before assembly.
- Install the new Woodruff key, then slide the new impeller onto the driveshaft while twisting it in the direction of engine rotation so the blades seat correctly.
- Install the new wear plate, O-rings, and seal, then reinstall the water-pump housing.
- Lightly grease the driveshaft splines and reinstall the lower unit, ensuring that the water tube and shift shaft align correctly.
Troubleshooting & FAQ
Will this kit fit my 5 HP Mercury outboard?
No. This kit is listed for the specific 4, 4.5, 6, 7.5, and 9.8 HP applications shown in the compatibility table. It is not listed for 5 HP Mercury or Mariner engines. Verify the horsepower, model, year, and serial number before ordering.
Is the impeller shaft size important?
Yes. This impeller is specified for an 11.0 mm (0.456-inch) driveshaft diameter. An incorrect size can prevent proper water-pump operation and may contribute to overheating or engine damage.
Why is my engine’s serial number important?
Manufacturers may change water-pump components during a model-year or production run. This kit is listed only for the serial-number ranges shown in the compatibility table, so check the engine identification label before ordering.
When should I replace my water-pump impeller?
Replace the impeller according to the engine manufacturer’s maintenance schedule and inspect it regularly. Frequent operation in saltwater, sand, or silt can accelerate wear.
What are the signs of a failing water-pump impeller?
Common symptoms include a weak or missing telltale stream, an overheating warning, or an impeller that is brittle, cracked, deformed, or missing blades during inspection.
Is this an OEM part or an aftermarket one?
This is an aftermarket replacement kit, not a Mercury OEM component. It is supplied as a replacement for the listed application and reference numbers.
How fast do you ship and what is the cost?
Typical worldwide transit is 5–15 days. Standard shipping is free, and available expedited options are shown at checkout.
What is the warranty and return policy?
This part is covered by a 1-year warranty against manufacturing defects under normal use. Contact support with your order details if an issue arises. Returns are accepted within the standard return window for unused items in their original condition. Refer to the applicable policy for complete instructions.
Safety & Important Info
- Verify the engine model, year, horsepower, stroke, serial-number range, and original-part dimensions before ordering.
- Compare the supplied parts with the original components before installation. Do not install the kit if the parts differ from the required application.
- This is an aftermarket replacement kit, not an OEM component.
- Professional installation is recommended for safe and reliable performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts designed for demanding real-world conditions.
- Fast Global Fulfillment — Free standard delivery is available to most regions, typically within 5–15 days.
- Manufacturer-Direct Value — Fair pricing supported by careful material selection and quality control.
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