Water Pump Impeller Kit – Fits Mercury/Mariner/Force 25-50 HP (Replaces 821354A2, 821354A1)
Water Pump Impeller Kit – Fits Mercury/Mariner/Force 25-50 HP (Replaces 821354A2, 821354A1) 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/Mariner/Force 25-50 HP (Repl...
Product Details
This Water Pump Impeller Kit provides a comprehensive solution for servicing the cooling system on Mercury/Mariner 25–50 HP, 4-stroke outboards (1998–Up) and Force 40–50 HP outboards (1995–1997). It is engineered to restore cooling efficiency and prevent engine overheating.
This kit serves as a direct cross-reference for Mercury part numbers 821354A1, 821354A2, and 821354A04, as well as aftermarket equivalents like Sierra 18-4531 and GLM 12045.
- Installs in the lower unit of the outboard motor.
- Designed for reliable performance in both fresh and saltwater environments.
- Manufactured with a durable neoprene impeller and stainless steel wear plate for extended service life.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket suppliers.
| Brand | Part Number | Superseded By | Notes |
|---|---|---|---|
| Mercury | 821354A1 | 821354A2 | |
| Mercury | 821354A04 | 821354A2 | |
| Mercury | 821354A2 | Current OEM Part | |
| Sierra | 18-4531 | Aftermarket Interchange | |
| GLM | 12045 | Aftermarket Interchange |
Engine & Model Compatibility
Confirm your engine model and year in the table below. Verifying serial numbers is recommended for an exact match.
Mercury/Mariner: This kit is designed for a variety of 2-stroke and 4-stroke models ranging from 25 HP to 50 HP. Check the serial number ranges listed in the 'Notes' column to ensure precise compatibility.
Force: Fits 40 HP and 50 HP 2-stroke outboards from 1995–1997 within the specified serial number range.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 25 HP | 25 | 4-Stroke | 1998–Up | 821354A1/A2 | Carb 0G590000 - 0T408999 |
| Mercury | 30 HP | 30 | 4-Stroke | 1998–Up | 821354A1/A2 | Carb 0G760300 - 0T408999 |
| Mercury | 30 HP | 30 | 4-Stroke | 1998–Up | 821354A1/A2 | Jet 0G590000 - Up |
| Mercury | 30 HP | 30 | 2-Stroke | 1994–2007 | 821354A1/A2 | 2 Cyl, 0G053314 - Up |
| Mercury | 40 HP | 40 | 2-Stroke | 1994–2007 | 821354A1/A2 | 2 Cyl, 0G053314 - Up |
| Mercury | 40 HP | 40 | 4-Stroke | 1998–Up | 821354A1/A2 | Four Stroke 2:1 0G760300 - 0T408999 |
| Mercury | 40 HP | 40 | 2-Stroke | 1997–2005 | 821354A1/A2 | 3 Cyl, 0G531301 - Up |
| Mercury | 45 HP | 45 | 4-Stroke | 1995–2000 | 821354A1/A2 | Bodensee 0G231123 - Up |
| Mercury | 50 HP | 50 | 2-Stroke | 1998–Up | 821354A1/A2 | 3 Cyl, 0G590000 - Up |
| Mercury | 50 HP | 50 | 4-Stroke | 1995–2008 | 821354A1/A2 | 0G231123 - Up |
| Mercury | 50 HP | 50 | 4-Stroke | 1995–2000 | 821354A1/A2 | Bigfoot |
| Force | 40 HP | 40 | 2-Stroke | 1995–1997 | 821354A1/A2 | 0E093700 - 0E287999 |
| Force | 50 HP | 50 | 2-Stroke | 1995–1997 | 821354A1/A2 | 0E093700 - 0E287999 |
Technical Specs
- Product Type
- Water Pump Impeller Kit
- Installation Location
- Lower Unit
- Wear Plate Material
- Stainless Steel
- Component Materials
- Neoprene Impeller, Nylon PA66 Tube, Non-asbestos Gasket
- Weight
- 150 g (5.3 oz)
- Compatible Environment
- For fresh and salt water use
What’s in the Box
- 1 x Water Pump Impeller (47-85089-10)
- 1 x Drive Key (85119)
- 1 x Wear Plate (8213542)
- 1 x Gasket, Upper (27-822189)
- 1 x Gasket, Lower (27-822217)
- 1 x Tube Seal, Short (43023)
- 1 x Tube Seal, Long (823547-1)
- 2 x Washers (12-86645)
Installation Notes
- Disconnect the battery and shift the outboard into neutral before beginning work.
- Place a drain pan under the lower unit and remove the drain/fill screws to empty the gearcase lubricant.
- Remove the bolts that secure the lower unit (gearcase) to the upper driveshaft housing.
- Carefully lower and separate the gearcase assembly from the outboard.
- Unbolt and remove the water pump housing cover to access the impeller. Note the rotational direction of the existing impeller vanes.
- Remove the old impeller, drive key, wear plate, gaskets, and seals. Thoroughly clean all mating surfaces.
- Install the new wear plate, gaskets, and seals provided in the kit.
- Apply a light coat of grease to the driveshaft and slide the new impeller on while turning the shaft clockwise to correctly orient the vanes. Install the new drive key.
- Reinstall the water pump housing, ensuring all seals are correctly seated. Torque the housing bolts to manufacturer specifications.
- Guide the gearcase back into position, ensuring the driveshaft, shift shaft, and water tube are properly aligned. Secure it by tightening the bolts to spec.
- Refill the gearcase with the correct type and amount of fresh marine lubricant.
- Reconnect the battery. Using a water supply (flushing muffs), start the engine and confirm a steady, strong stream of water from the tell-tale outlet.
Troubleshooting & FAQ
How can I be sure this impeller kit fits my specific engine?
This kit fits a wide range of Mercury, Mariner, and Force models. For a guaranteed match, please compare your engine's model, horsepower, year, and serial number against the detailed compatibility tables provided on this page. When in doubt, checking the serial number is the most reliable method.
What are the common signs that my water pump impeller needs replacement?
Common symptoms include the engine overheating (especially at idle or low speeds), a weak or intermittent water stream from the "tell-tale" cooling outlet, and, upon inspection, an old impeller that is cracked, brittle, or has deformed or missing vanes.
How often should I replace the water pump impeller?
For preventative maintenance and to ensure engine longevity, it is recommended to replace the impeller every 100-200 operating hours or at least once a year, regardless of use. Service intervals should be shorter if you frequently operate in sandy or silty water.
Does this kit include the full water pump housing?
No, this is an impeller repair and service kit. It includes all the necessary wear items for a standard service: the impeller, drive key, stainless steel wear plate, gaskets, and seals. The main pump housing is not part of this kit and should be inspected for wear or cracks separately.
Is this an OEM part or an aftermarket equivalent?
This is a high-quality aftermarket replacement part, not an OEM component. It is engineered to meet or exceed original equipment specifications for fit, form, and function and is manufactured in an ISO 9001 certified facility to ensure consistent quality.
What are your shipping speeds and costs?
We ship worldwide quickly—typical transit time is 5–15 days for most regions. Standard shipping is free on all orders. Expedited shipping options, if available for your location, will be presented at checkout.
What is the warranty and return policy for this part?
This product is covered by a 1-year warranty against manufacturing defects under normal use conditions. If you encounter any issues, please contact our support team with your order details. We accept returns for unused items in their original packaging within our standard return window. Please see our dedicated policy page or contact us for instructions.
Safety & Important Info
- Verify images and specifications against your original part before purchase. If anything appears different—even if your model is listed as compatible—do not proceed with the installation and contact us for support.
- This is an aftermarket replacement component, not an Original Equipment Manufacturer (OEM) part. All mentions of brand names and part numbers are for reference purposes only.
- Professional installation is highly recommended to ensure safety, proper function, and optimal engine performance. Incorrect installation can lead to severe engine damage.
About Sea Sierra
- Pro-Grade Standards — We supply professional-grade marine parts engineered to meet or exceed OEM tolerances and rigorously tested for real-world performance and durability.
- Fast Global Fulfillment — With warehouses worldwide, we offer free standard delivery to most regions, typically arriving in just 5–15 days.
- Manufacturer-Direct Value — By eliminating layers of distribution, we deliver exceptional value and fair pricing without ever compromising on materials or quality control.
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