Water Pump Repair Kit – Fits Mercury/Mariner 25-50HP (Replaces Mercury 821354A2)
Water Pump Repair Kit – Fits Mercury/Mariner 25-50HP (Replaces Mercury 821354A2) 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
Free standard shipping on all orders under 1 KG
Water Pump Repair Kit – Fits Mercury/Mariner 25-50HP (Replaces Merc...
Product Details
This Water Pump Repair Kit – Fits Mercury/Mariner 25-50HP Outboards (Replaces 821354A2) is designed to restore the cooling system performance of your engine. It provides a direct fit for Mercury/Mariner 25-50HP 2-stroke and 4-stroke outboards from 1994–2018, as well as Force 40-50HP 2-stroke engines from 1995–1997.
This kit serves as a direct cross-reference for Mercury parts 821354A2, 821354A1, and 821354A04. It also interchanges with Sierra 18-4531, GLM 12045, Pro Marine 3219/3219-1, and SEI Marine 96-265-03BK.
- Engineered as a direct OEM-equivalent replacement for a perfect fit.
- Constructed with a durable neoprene impeller and a stainless steel 316 wear plate for corrosion resistance.
- Includes all necessary gaskets, seals, and hardware for a complete overhaul.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket suppliers.
| Brand | Part Number |
|---|---|
| Mercury | 821354A2 |
| Mercury | 821354A1 |
| Mercury | 821354A04 |
| Sierra | 18-4531 |
| GLM | 12045 |
| Pro Marine | 3219 |
| Pro Marine | 3219-1 |
| SEI Marine | 96-265-03BK |
Engine & Model Compatibility
Confirm your engine model and year in the tables below to ensure proper fitment.
Mercury/Mariner Outboard Applications
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury/Mariner | 25 | 25 | 4-Stroke | 1998–2018 | 821354A2 | Carb 0G590000–0T408999 |
| Mercury/Mariner | 30 | 30 | 2-Stroke | 1994–2018 | 821354A2 | 2 Cylinder models |
| Mercury/Mariner | 30 | 30 | 4-Stroke | 1998–2018 | 821354A2 | |
| Mercury/Mariner | 30 Jet | 30 | 4-Stroke | 1998–2018 | 821354A2 | 3 Cylinder models |
| Mercury/Mariner | 40 | 40 | 2-Stroke | 1994–2018 | 821354A2 | 2 & 3 Cylinder models |
| Mercury/Mariner | 40 | 40 | 4-Stroke | 1998–2018 | 821354A2 | |
| Mercury/Mariner | 45 Bodensee | 45 | 4-Stroke | 1998–2018 | 821354A2 | Special emission models |
| Mercury/Mariner | 50 | 50 | 2-Stroke | 1998–2018 | 821354A2 | 3 Cylinder models |
| Mercury/Mariner | 50 | 50 | 4-Stroke | 1998–2018 | 821354A2 | |
| Mercury/Mariner | 50 Bigfoot | 50 | 4-Stroke | 1998–2018 | 821354A2 |
Force Outboard Applications
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Force | 40 | 40 | 2-Stroke | 1995–1997 | 821354A2 | Serial: 0E093700–0E287999 |
| Force | 50 | 50 | 2-Stroke | 1995–1997 | 821354A2 | Serial: 0E093700–0E287999 |
Technical Specs
- Product Type
- Water Pump Repair Kit
- Installation
- Direct OEM Replacement
- Housing Material
- Stainless Steel 316 (Plate)
- Impeller Material
- Neoprene Rubber
- Tube Material
- Nylon PA66
- Dimensions
- 152.4 × 114.3 × 38.1 mm (6 × 4.5 × 1.5 in) [packaging]
- Weight
- 0.18 kg (5.3 oz)
- Warranty
- 1 Year
What’s in the Box
- 1 × Water Pump Impeller (47-85089/8508910/850893)
- 1 × Impeller Key (85119)
- 1 × Face Plate/Wear Plate (12505/8213542)
- 1 × Gasket Upper (27-822189)
- 1 × Gasket Lower (27-822217)
- 1 × Tube Seal (85180/43023)
- 1 × Tube Seal (85181/823547-1)
- 2 × Washer (31175/12-86645-1)
Installation Notes
- Disconnect the battery and remove the engine cover.
- Drain the gearcase lubricant from the lower unit.
- Remove the bolts securing the lower unit (gearcase) to the engine's midsection and carefully lower it.
- Locate the water pump housing, typically found on top of the gearcase, and remove its mounting bolts.
- Remove the old housing, impeller, wear plate, gaskets, and seals. Clean all mating surfaces thoroughly.
- Install the new gaskets, wear plate, impeller key, and impeller. Ensure the impeller vanes are oriented correctly (typically by turning the driveshaft clockwise).
- Lightly grease the inside of the new housing and install it over the impeller.
- Replace all seals and reassemble the water pump unit, tightening bolts to the manufacturer's specified torque.
- Reinstall the lower unit, ensuring the water tube, shift shaft, and driveshaft align correctly.
- Refill the gearcase with fresh lubricant, reconnect the battery, and test the engine using a water supply (flushing muffs) to verify cooling system operation.
Troubleshooting & FAQ
How do I know if my water pump is failing?
Common signs include a weak or intermittent water stream from the tell-tale port, engine overheating alarms, and visible steam from the exhaust. A physical inspection might reveal a stiff, cracked, or damaged impeller with worn or missing vanes.
Will this kit fit my specific engine serial number?
This kit is designed for the specified HP and year ranges. For Force engines, it fits serials 0E093700–0E287999. For Mercury 25 HP 4-Strokes, it fits carb models from 0G590000 to 0T408999. For other models, it is best to verify fitment by visual comparison or by consulting your engine’s service manual with the OEM part number 821354A2.
How often should a water pump impeller be replaced?
As a preventative maintenance item, most manufacturers recommend replacing the water pump impeller every 1-2 years or every 100-200 hours of operation, whichever comes first. Usage in saltwater or sandy/silty conditions may require more frequent replacement.
What is the difference between the materials used in this kit and the OEM version?
This kit uses materials designed to meet or exceed OEM specifications. The impeller is made from durable neoprene rubber for flexibility and longevity, while the wear plate is made of Stainless Steel 316 for enhanced corrosion resistance in marine environments.
Is this a complete kit, or do I need other parts?
This is a comprehensive repair kit containing the impeller, key, wear plate, gaskets, and seals required for a standard water pump service. No other components are typically needed unless the pump housing itself is cracked or severely corroded.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). It is built to OEM-level specifications with comparable materials and manufactured in an ISO 9002 facility, with batch inspections for consistency.
Shipping speed & cost
We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free, and expedited options will appear at checkout where available.
Warranty & returns
This product is covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact our support team with your order details. Returns are accepted within our standard window for unused items in their original condition. See our policy page or reach out for instructions.
Safety & Important Info
- Verify images and specifications against your original part before purchase. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement part, not an OEM component.
- Professional installation is recommended for safety and optimal performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world conditions.
- Fast Global Fulfillment — We offer free standard delivery to most regions, with typical transit times of 5–15 days.
- Manufacturer-Direct Value — By working directly with manufacturers, we provide fair pricing without compromising on materials or quality control.
Payment & Security
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