Water Pump Impeller Kit – Fits MerCruiser Alpha One Gen 2 & Mercury Marine 200-250 HP Outboards (Replaces 817275A5, 817275Q05)
Water Pump Impeller Kit – Fits MerCruiser Alpha One Gen 2 & Mercury Marine 200-250 HP Outboards (Replaces 817275A5, 817275Q05) 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 MerCruiser Alpha One Gen 2 & Mer...
Product Details
This Water Pump Impeller Kit – Fits MerCruiser Alpha One Gen 2 & Mercury Marine 200-250 HP Outboards (Replaces 817275A5, 817275Q05) is engineered for Mercury Marine and Mariner 200–250 HP (3.0L) DFI/EFI outboards as well as MerCruiser Alpha One Gen 2 sterndrives from 1991 to the present. The kit includes all necessary components for a complete water pump assembly replacement, ensuring proper cooling system function.
It serves as a direct replacement for Mercury Marine 817275A5; MerCruiser 817275K05, 817275Q05, 817275A6, 817275A4, 817275T4, and 817275Q4; Sierra 18-3147; and Mallory 9-48315.
- Designed for a vehicle-specific fit in compatible marine engines.
- Constructed with a durable neoprene impeller and stainless steel housing components.
- Includes a complete set of gaskets, seals, and O-rings for a full service.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket brands.
| Brand | Part Number |
|---|---|
| Mercury Marine | 817275A5 |
| MerCruiser | 817275K05 / 817275Q05 / 817275A6 / 817275A4 / 817275T4 / 817275Q4 |
| Sierra | 18-3147 |
| Mallory | 9-48315 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Mercury and Mariner outboards, verify your engine's serial number falls within the specified range to ensure an exact match.
For MerCruiser applications, this kit is designed for Alpha One Generation 2 sterndrives manufactured from 1991 to present.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury/Mariner | 200 DFI | 200 | 4-Stroke | Up to 2008 | 817275A5 | Serial: 0G590000-0T800999 |
| Mercury/Mariner | 200 DFI (3.0L) | 200 | 4-Stroke | Up to 2010 | 817275A5 | Serial: 0T801000-1B504988 |
| Mercury | 200 DFI (3.0L)(DTS) | 200 | 4-Stroke | Up to 2010 | 817275A5 | Serial: 0T980000-1B504988 |
| Mercury/Mariner | 200 EFI (3.0L) | 200 | 4-Stroke | Up to 2010 | 817275A5 | Serial: 0T750164-1B504988 |
| Mercury/Mariner | 225 Carb (3.0L) | 225 | 4-Stroke | Up to 2006 | 817275A5 | Serial: 0G760300-0T408999 |
| Mercury/Mariner | 225 DFI | 225 | 4-Stroke | Up to 2010 | 817275A5 | Serial: 0G590000-1B504988 |
| Mercury/Mariner | 225 DFI (3.0L) | 225 | 4-Stroke | Up to 2010 | 817275A5 | Serial: 0T801000-1B504988 |
| Mercury/Mariner | 225 DFI (3.0L)(DTS) | 225 | 4-Stroke | Up to 2010 | 817275A5 | Serial: 0T599000-1B504988 |
| Mercury/Mariner | 225 EFI (3.0L) | 225 | 4-Stroke | Up to 2010 | 817275A5 | Serial: 0G760300-1B504988 |
| Mercury/Mariner | 225 EFI (3.0L) Seapro/Marathon | 225 | 4-Stroke | Up to 2009 | 817275A5 | Serial: 0T801000-1B417701 |
| Mercury | 225 PRO XS DFI (3.0L) | 225 | 4-Stroke | Up to 2009 | 817275A5 | Serial: 1B104549-1B426560 |
| Mercury/Mariner | 225 Seapro/Marathon Carb (3.0L) | 225 | 4-Stroke | Up to 2006 | 817275A5 | Serial: 0G760300-0T408999 |
| Mercury/Mariner | 250 EFI (3.0L) | 250 | 4-Stroke | Up to 2010 | 817275A5 | Serial: 0G760300-1B504988 |
| Mercury | 250XB EFI (3.0L) | 250 | 4-Stroke | Up to 2008 | 817275A5 | Serial: 0G980600-0T800999 |
| Mercury/Mariner | 3.0L EFI Seapro/Marathon | 200–250 | 4-Stroke | Up to 2008 | 817275A5 | Serial: 0T409000-0T800999 |
| Brand | Model | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|
| MerCruiser | Alpha One Gen 2 | 4-Stroke | 1991–Present | 817275K05 / Q05 | Sterndrive application |
Technical Specs
- Product Type
- Water Pump Impeller Kit with Housing
- Installation
- Vehicle-specific fit
- Fuel Type
- Gasoline
- Housing Material
- Stainless Steel Wear Plate and Housing
- Impeller Material
- Neoprene
- Gasket Material
- Non-asbestos
- Weight
- 0.72 kg (1.59 lb)
- Other Technical Attributes
- Includes complete water pump assembly parts
What’s in the Box
- 1 x Carrier Seal (821759A4)
- 1 x Impeller (47-43026T2)
- 1 x Impeller Plate (8172761)
- 1 x Impeller Key (28-43037)
- 2 x O-Ring (25-21836)
- 1 x Seal Ring Gasket (26-45577B1)
- 1 x Face Seal and Tool (26-816575A2)
- 1 x Impeller Gasket (27-430331)
- 1 x Impeller Gasket (27-8172771)
- 1 x Drain Screw Gasket (12-191833)
Installation Notes
- Disconnect the battery and shift the engine into neutral.
- Place a drain pan under the lower unit and remove the gearcase oil drain/fill screws to drain the oil.
- Remove the bolts securing the lower unit (gearcase) to the upper housing. Note the location of any different-sized bolts.
- Carefully lower the gearcase, disengaging the shift shaft and driveshaft.
- Unbolt and remove the old water pump housing and impeller assembly.
- Clean the mounting surfaces thoroughly, removing any old gasket material or sealant.
- Assemble the new kit components in order, applying a light coat of marine grease to the new impeller and housing interior. Ensure the impeller key is correctly seated.
- Install the new water pump assembly onto the driveshaft, ensuring the impeller vanes are oriented correctly (typically by turning the driveshaft clockwise).
- Reinstall the lower unit, aligning the driveshaft, water tube, and shift shaft.
- Secure the gearcase with the bolts, tightening them to the manufacturer's specified torque.
- Refill the gearcase with fresh marine gear oil and reinstall the battery cables.
- Start the engine in the water or with a proper flushing attachment to verify correct cooling system operation.
Troubleshooting & FAQ
How do I know if this kit fits my engine?
The most reliable method is to check your engine's model, year, and serial number against the compatibility tables on this page. For Mercury/Mariner outboards, the serial number range is critical. For MerCruiser, confirm you have an Alpha One Gen 2 sterndrive (1991 or newer).
What are the signs of a bad water pump impeller?
Common symptoms include the engine overheating at idle or low speeds, a weak or non-existent "telltale" water stream, or a brittle, cracked, or deformed impeller upon inspection. Reduced boat performance can also be an indicator.
How often should I replace the water pump impeller?
As a general maintenance guideline, it is recommended to replace the impeller every 100 operating hours or at least once every two years, whichever comes first. This interval can be shorter if you frequently operate in sandy, silty, or saltwater conditions.
Is the face seal installation tool included?
Yes, this kit includes the face seal and the corresponding installation tool (Part No. 26-816575A2) to ensure proper seating and prevent damage during installation.
My sterndrive is an Alpha One, but how do I know if it's Gen 1 or Gen 2?
Alpha One Gen 2 drives, which this kit fits, began production in 1991. They can be distinguished by their water pump housing, which is located on the lower unit. Gen 1 drives have the water pump located in the upper housing. Visually, Gen 2 drives also have a more rounded, streamlined shape and typically feature a through-prop exhaust.
What's the difference between OEM and this aftermarket part?
This listing is an aftermarket replacement (not OEM). It is built to OEM-level specifications with comparable materials, such as a neoprene impeller and stainless steel housing. Our parts are manufactured in an ISO 9002 facility and are batch-inspected for consistency and quality.
How fast do you ship and what does it cost?
We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free to most locations, with expedited options available at checkout where applicable.
What is your warranty and return policy?
This kit is covered by a 1-year warranty against manufacturing defects under normal use. If you encounter any issues, please contact our support team with your order details. Returns are accepted within our standard window for unused parts in their original condition. See our policy page or reach out for instructions.
Safety & Important Info
- Verify images and specifications against 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 quality control.
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