Water Pump Repair Kit for Mercury/Mariner 25–50 HP Outboards — Replaces 821354A2, 821354A1 and 821354A04
Water Pump Repair Kit for Mercury/Mariner 25–50 HP Outboards — Replaces 821354A2, 821354A1 and 821354A04 is backordered and will ship as soon as it is back in stock.
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Water Pump Repair Kit for Mercury/Mariner 25–50 HP Outboards — Repl...
Water Pump Repair Kit for Mercury/Mariner 25–50 HP Outboards — Replaces 821354A2, 821354A1 and 821354A04 is backordered and will ship as soon as it is back in stock.
Product Details
This water pump repair kit is intended to service the cooling-system water pump on listed Mercury and Mariner 25–50 HP outboards. The kit is designed to replace commonly referenced water-pump components and may help restore proper water circulation when the impeller, wear plate, gaskets or seals are worn. Replacing these service parts as a set can help reduce the risk of cooling-system leaks and overheating caused by damaged pump components.
This is an aftermarket replacement kit associated with Mercury references 821354A2, 821354A1 and 821354A04. Additional aftermarket references commonly associated with this application include Sierra 18-4531, GLM 12045 and SEI 3219. Confirm the part number, engine configuration and serial-number range before ordering.
- Service kit for the lower-unit water pump.
- Includes an impeller, wear plate, gaskets, seals, washers and drive key as listed below.
- Suitable for listed Mercury, Mariner and Force applications when the model and serial-number conditions match.
- For freshwater or saltwater use with appropriate marine service and maintenance practices.
Part Number Matrix
The following references are provided for identification and cross-reference purposes. They are not a substitute for confirming the exact engine model and serial-number range.
| Brand | Part Number |
|---|---|
| Mercury | 821354A2 |
| Mercury | 821354A1 |
| Mercury | 821354A04 |
| Sierra | 18-4531 |
| GLM | 12045 |
| SEI | 3219 |
Engine and Model Compatibility
The applications below reflect the listed fitment information for this repair kit. Keep the engine model, horsepower, stroke, year and serial-number range together when checking compatibility. A similar horsepower rating alone does not confirm fitment.
| Brand | Model | Rated HP | Stroke | Years | Reference Part No. | Serial or Model Notes |
|---|---|---|---|---|---|---|
| Mercury/Mariner | Four Stroke | 25 | 4-Stroke | 1998–2018 | 821354A2 | Carbureted models, 0G590000–0T408999 |
| Mercury/Mariner | Four Stroke | 30 | 4-Stroke | 1998–2018 | 821354A2 | Carbureted models, 0G760300–0T408999 |
| Mercury/Mariner | Four Stroke | 30 | 4-Stroke | 1998–2018 | 821354A2 | Jet models, 0G590000 and later |
| Mercury/Mariner | Two Cylinder | 30/40 | 2-Stroke | 1998–2018 | 821354A2 | 0G053314 and later |
| Mercury/Mariner | Four Stroke | 40/45 | 4-Stroke | 1998–2018 | 821354A2 | 2:1 models, 0G760300–0T408999 |
| Mercury/Mariner | Four Stroke | 45 | 4-Stroke | 1998–2018 | 821354A2 | Bodensee models, 0G231123 and later |
| Mercury/Mariner | Three Cylinder | 40 | 2-Stroke | 1998–2018 | 821354A2 | 0G531301 and later |
| Mercury/Mariner | Three Cylinder | 50 | 2-Stroke | 1998–2018 | 821354A2 | 0G590000 and later |
| Mercury/Mariner | Four Stroke | 50 | 4-Stroke | 1998–2018 | 821354A2 | 0G231123 and later |
| Mercury/Mariner | BigFoot | 50 | 4-Stroke | 1998–2018 | 821354A2 | 0G760300–0T178499 |
Force Applications
The kit is also listed for select 2-stroke Force outboards. Verify the complete model and serial-number range before installation.
| Brand | Model | Rated HP | Stroke | Years | Reference Part No. | Serial Range |
|---|---|---|---|---|---|---|
| Force | Outboard | 40 | 2-Stroke | 1995–1997 | 821354A2 | 0E288000–0E369299 |
| Force | Outboard | 50 | 2-Stroke | 1995–1997 | 821354A2 | 0E288000–0E369299 |
Technical Specifications
- Product Type
- Water pump repair kit
- Application
- Lower-unit water pump service
- Installation
- Replacement service parts for the water-pump assembly
- Impeller Material
- Neoprene rubber
- Plate Material
- Metal alloy
- Fitting Type
- Direct-replacement style; verify the original parts and engine serial number before installation
- Reference Mercury Part Numbers
- 821354A2, 821354A1 and 821354A04
- Aftermarket Cross-References
- Sierra 18-4531, GLM 12045 and SEI 3219
What's in the Box
- 1 × Neoprene impeller — references 47-85089-10 and 47-85089-3
- 1 × Wear plate — reference 8213542
- 1 × Upper gasket — reference 27-822189
- 1 × Lower gasket — reference 27-822217
- 1 × Short water-tube seal — reference 43023
- 1 × Long water-tube seal — references 823547-1 and 8235471
- 2 × Washer — reference 12-86645-1
- 1 × Drive key — reference 85119
Package contents are based on the listed kit configuration. Compare the supplied components with the parts removed from your engine before beginning installation.
Installation Notes
- Disconnect the battery and follow the engine manufacturer's safety procedures.
- Drain the gearcase oil if required for removal of the lower unit.
- Remove the fasteners securing the lower unit and carefully lower the unit from the engine.
- Remove the water-pump housing and retain hardware that will be reused.
- Remove the old impeller, gaskets, wear plate, seals and drive key. Clean the mating surfaces and inspect the housing, driveshaft and water tube.
- Install the new wear plate, gaskets, seals and drive key in the correct order for the engine model.
- Install the impeller on the driveshaft, orienting the vanes in the direction specified by the engine service information.
- Reinstall the water-pump housing and make sure the seals are correctly seated.
- Reattach the lower unit while aligning the driveshaft, shift mechanism and water tube.
- Refill the gearcase with the correct lubricant and reconnect the battery.
- Run the engine only with an appropriate water supply, such as flushing muffs or a test tank, and confirm a steady tell-tale stream.
Installation procedures can vary by model. Use the applicable factory service information and correct tightening specifications for your engine.
Troubleshooting and FAQ
How can I confirm whether this kit fits my engine?
Match the engine brand, model, horsepower, stroke, year and serial-number range to the compatibility tables. Also compare the original impeller, wear plate, gaskets, seals and drive key with the listed kit contents. If any of these details differ, obtain model-specific confirmation before ordering.
What are common signs of a worn water-pump impeller?
Common signs include a weak or intermittent tell-tale stream, an overheating warning, elevated operating temperature or visible cracking, missing vanes or hardening of the old impeller. Inspect the complete pump assembly rather than replacing the impeller alone when other components are worn.
How often should the impeller be replaced?
Inspection and replacement intervals depend on the engine manufacturer, operating hours and water conditions. Sandy, silty or saltwater operation can accelerate wear. Follow the maintenance schedule for your specific engine and replace the impeller whenever it shows damage or loss of flexibility.
Should lubricant be used during installation?
Use only a lubricant or installation method approved for the impeller and water-pump housing. A suitable water-based solution can help during initial assembly; avoid products that may damage neoprene or contaminate the cooling system.
Is this an OEM part?
No. This listing is for an aftermarket replacement kit. Mercury, Mariner, Force, Sierra, GLM and SEI references are provided for identification and cross-reference purposes only; the kit is not represented as a genuine OEM product.
Safety and Important Information
- Confirm the complete engine model and serial-number range before purchase.
- Compare the original parts and the supplied components before installation.
- Do not operate the engine without an adequate water supply.
- Inspect the water-pump housing, driveshaft, water tube and mating surfaces during service.
- Professional installation is recommended when the correct procedure or model-specific service information is unavailable.
About Sea Sierra
- Marine Replacement Parts — Replacement components for routine outboard maintenance and repair.
- Application-Focused Listings — Product references and compatibility information are provided to help match the part to the correct engine configuration.
- Service-Ready Kits — Packaged components help simplify routine water-pump service when the listed application and contents match the engine.
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