Water Pump Impeller Kit – Fits Mercury/Mariner 3.5-9.8 HP (Replaces 47-89980T1, 89980Q1)
Water Pump Impeller Kit – Fits Mercury/Mariner 3.5-9.8 HP (Replaces 47-89980T1, 89980Q1) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Water Pump Impeller Kit – Fits Mercury/Mariner 3.5-9.8 HP (Replaces...
Water Pump Impeller Kit – Fits Mercury/Mariner 3.5-9.8 HP (Replaces 47-89980T1, 89980Q1) is backordered and will ship as soon as it is back in stock.
Product Details
This Water Pump Impeller Kit is designed for Mercury/Mariner 3.5–9.8 HP 1-cylinder 2-Stroke outboards manufactured between 1979 and 1986. It is specifically engineered for models requiring an impeller with a 0.438-inch inner diameter, ensuring reliable cooling performance and engine protection.
It serves as a direct replacement for multiple OEM and aftermarket part numbers, including Mercury 47-89980T1, Mercury 89980Q1, Mercury/Mariner 47-89980Q1, and Sierra 18-3446.
- Engineered as a direct-fit replacement for straightforward installation.
- The impeller is constructed from a durable neoprene/rubber compound for longevity.
- Kit includes essential wear plates, O-rings, and seals for a complete service.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 47-89980T1 |
| Mercury | 89980Q1 |
| Mercury/Mariner | 47-89980Q1 |
| Sierra | 18-3446 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury/Mariner | Outboard | 9.8 | 2-Stroke | 1979–1985 | 47-89980T1/89980Q1 | 0.438" Imp. ID |
| Mercury/Mariner | Outboard | 7.5 | 2-Stroke | 1979–1986 | 47-89980T1/89980Q1 | 0.438" Imp. ID |
| Mercury/Mariner | Outboard | 4.5 | 2-Stroke | 1980–1985 | 47-89980T1/89980Q1 | 1-Cyl, 0.438" Imp. ID |
| Mercury/Mariner | Outboard | 4 | 2-Stroke | 1982–1986 | 47-89980T1/89980Q1 | 1-Cyl, 0.438" Imp. ID |
Technical Specs
- Product Type
- Water Pump Impeller Kit
- Installation
- Direct replacement
- Impeller Material
- Neoprene/rubber compound
- Impeller ID
- 0.438" (11.13 mm)
- Impeller Hub Width/Height
- 14.4 mm
- Number of Blades
- 6
- Operating Temperature
- Up to 105°C (221°F)
- Warranty
- 1 Year (varies by seller)
What’s in the Box
- 1 x Sleeve (700-12963)
- 1 x Impeller (700-89800)
- 1 x Wear Plate (700-12560)
- 1 x O-Ring (700-81230)
- 1 x O-Ring (700-81090)
- 1 x Seal (700-85651)
Installation Notes
- Disconnect the spark plug leads and battery cables for safety.
- Position a drain pan and remove the gearcase drain and vent screws to drain the lower unit oil.
- Remove the bolts securing the lower unit (gearcase) to the engine midsection.
- Carefully lower the gearcase to access the water pump housing.
- Remove the water pump housing bolts and slide the housing up to expose the old impeller.
- Remove the old impeller, key, gaskets, and wear plate, noting their orientation.
- Clean all mating surfaces thoroughly, removing any old gasket material or debris.
- Install the new wear plate, gaskets, and seals provided in the kit.
- Slide the new impeller onto the driveshaft. Lubricate the housing interior and turn the driveshaft clockwise to seat the blades correctly.
- Reinstall the water pump housing, ensuring all seals are correctly positioned, and tighten bolts to the manufacturer's specified torque.
- Reattach the lower unit to the engine, refilling it with fresh gear oil before tightening the screws.
- Reconnect the battery and spark plugs. Start the engine in water and verify a steady stream of water from the tell-tale outlet.
Troubleshooting & FAQ
How do I confirm this kit fits my specific engine?
Verify that your engine is a Mercury/Mariner 3.5–9.8 HP 2-stroke model from the years listed in the compatibility table. A critical check is to confirm your old impeller has an inner diameter of 0.438 inches, as some models used different sizes.
What are the signs of a bad impeller?
Common symptoms include a weak or non-existent water stream from the "tell-tale" outlet, engine overheating alerts or steam from the exhaust, and a melted or warped water pump housing. Failure to replace a worn impeller can lead to severe engine damage.
How often should I replace my water pump impeller?
As a best practice, impellers should be replaced every 1-2 years or every 100-200 hours of operation, whichever comes first. For boats used in saltwater or sandy/silty conditions, annual replacement is strongly recommended to prevent premature failure.
Why does the old impeller look fine but the engine still overheats?
An impeller can lose its flexibility and "set" over time, even if it appears visually intact. This prevents the blades from flexing properly against the pump housing, reducing pumping efficiency. Material fatigue is not always visible to the naked eye.
Is anything else needed for installation?
This kit contains the core components. However, you will also need marine-grade grease for lubrication, gasket sealant (optional, but recommended by some mechanics), and fresh lower unit gear oil for refilling the gearcase after service.
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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