Water Pump Impeller Kit – Fits Mercury/Force/Mariner 15-25 HP (Replaces 47-85089T7, 47-85089Q4)
Water Pump Impeller Kit – Fits Mercury/Force/Mariner 15-25 HP (Replaces 47-85089T7, 47-85089Q4) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.
Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Water Pump Impeller Kit – Fits Mercury/Force/Mariner 15-25 HP (Repl...
Product Details
This Water Pump Impeller Kit – Fits Mercury/Force/Mariner 18-25 HP (Replaces 47-85089T7, 47-85089Q4) is designed for Mercury/Mariner 2-stroke outboard engines from 15–25 HP (1983–2006) and Force 18–25 HP 2-stroke outboards. It ensures your engine maintains proper cooling and prevents overheating.
This kit serves as a direct replacement for Mercury part numbers 47-85089T7 and 47-85089Q4, as well as the Sierra aftermarket equivalent 18-3215.
- Installation Method: Direct OEM-style replacement.
- Included Essentials: Contains the core components needed for a standard impeller replacement.
- Warranty: Backed by a Limited Lifetime Warranty (Sierra brand).
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 47-85089T7 |
| Mercury | 47-85089Q4 |
| Sierra | 18-3215 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This impeller kit fits a range of Mercury and Mariner 2-stroke outboards from 15 HP to 25 HP manufactured between 1983 and 2006.
It is also compatible with certain Force 18 HP to 25 HP 2-stroke outboard models.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| Mercury/Mariner | Various | 15-25 | 2-Stroke | 1983–2006 | 47-85089T7/47-85089Q4 |
| Force | Various | 18-25 | 2-Stroke | 47-85089T7/47-85089Q4 |
Technical Specs
- Product Type
- Water Pump Impeller Repair Kit
- Installation
- Direct OEM Replacement
- Warranty
- Limited Lifetime (Sierra brand)
What’s in the Box
- 1 x Water Pump Impeller Kit (replaces 47-85089T7/47-85089Q4)
Installation Notes
- Disconnect the negative battery cable and remove the propeller for safety.
- Drain the gearcase lube by removing the upper and lower drain screws.
- Unbolt and carefully lower the gearcase (lower unit) from the outboard's midsection.
- Remove the bolts securing the water pump housing to the gearcase.
- Slide the housing up and off the driveshaft, then remove the old impeller, wear plate, and gaskets.
- Thoroughly clean the mating surfaces of the gearcase and the inside of the pump housing.
- Install the new gaskets, wear plate, and impeller. Turn the driveshaft clockwise while pushing the impeller down to seat the vanes correctly.
- Reinstall the water pump housing and torque the bolts to the manufacturer's specified value.
- Apply a light coating of marine grease to the driveshaft splines and reinstall the lower unit.
- Refill the gearcase with the correct type and amount of marine gear lube.
- Reinstall the propeller and reconnect the battery.
- Start the engine using a water source (flushing muffs or in the water) and confirm a steady stream of water from the tell-tale outlet.
Troubleshooting & FAQ
How do I confirm this kit fits my engine?
This kit fits most Mercury/Mariner 15-25 HP (1983–2006) and Force 18-25 HP 2-stroke outboards. The most reliable way to confirm fitment is to match your engine's original part number to the cross-references provided: Mercury 47-85089T7, 47-85089Q4, or Sierra 18-3215.
What are the signs of a failing water pump impeller?
Key symptoms include a weak or intermittent water stream from the "telltale" port, engine overheating alarms, steam from the exhaust, or a melted water pump housing. Reduced engine performance can also be an indicator.
How often should I replace the impeller?
As a rule of thumb, replace the impeller every 1-2 years or every 100-200 hours of operation. More frequent replacement is recommended if you operate in sandy, silty, or saltwater environments.
Can I replace just the impeller instead of the whole kit?
While possible, it is highly recommended to replace all components in the kit (gaskets, seals, wear plate) at the same time. These parts wear together, and replacing only the impeller can lead to premature failure and poor sealing.
Is this kit difficult to install?
Installation is a common maintenance task for those with mechanical experience and the proper tools. It involves removing the lower unit. If you are not comfortable performing this service, professional installation is recommended.
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.
Payment & Security
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