Water Pump Impeller Repair Kit for Mercury 25–50 HP Outboards – Replaces 821354A2
Water Pump Impeller Repair Kit for Mercury 25–50 HP Outboards – Replaces 821354A2 is backordered and will ship as soon as it is back in stock.
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Water Pump Impeller Repair Kit for Mercury 25–50 HP Outboards – Rep...
Water Pump Impeller Repair Kit for Mercury 25–50 HP Outboards – Replaces 821354A2 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket water pump impeller repair kit is designed for selected Mercury 25–50 HP outboards using Mercury water pump repair kit part number 821354A2. The kit services the water pump assembly in the lower unit or gearcase and is intended to help restore proper cooling-water flow during routine water pump maintenance.
Mercury parts-catalog occurrences identify 821354A2 as a water pump repair kit in gear housing and driveshaft diagrams for selected 30, 40, 45, and 50 HP applications. Because fitment depends on model details, gear ratio, and serial-number range, always compare your engine model and serial number with the compatibility information below before ordering.
- For servicing the water pump assembly in the lower unit or gearcase.
- Includes an impeller, gaskets, seals, wear plate, washer, and drive key for the listed kit configuration.
- Aftermarket replacement; not manufactured or supplied by Mercury Marine.
- Install only after confirming that the replacement parts match the original components removed from your engine.
Part Number References
The primary catalog reference associated with the documented Mercury applications is shown below. Other numbers may be used by distributors or aftermarket brands for related products, but a number match alone does not confirm fitment for every engine configuration.
| Brand or source | Reference | Use |
|---|---|---|
| Mercury Marine | 821354A2 | Water pump repair kit reference found in Mercury gear housing and driveshaft catalogs |
| Aftermarket cross-reference | 18-4531 | Reference supplied for this aftermarket listing; verify against your original part and engine serial number |
| Aftermarket cross-reference | GLM 12045 | Reference supplied for this aftermarket listing; verify application before purchase |
Engine and Model Compatibility
The following applications are associated with water pump repair kit reference 821354A2 in the available Mercury parts-catalog data. The listed serial ranges and gear-housing conditions must be treated as part of the fitment specification; horsepower alone is not sufficient for selection.
| Brand | Model | Rated HP | Stroke | Serial or catalog condition | Water pump reference |
|---|---|---|---|---|---|
| Mercury | 30, 2-cylinder | 30 | Not specified in occurrence | 0G055314 through 0G760299; 2.00:1 gear ratio catalog | 821354A2 |
| Mercury | 30, 2-cylinder | 30 | Not specified in occurrence | 0G760300 through 0T979999; 2.00:1 gear ratio catalog | 821354A2 |
| Mercury | 30 Jet | 30 | Not specified in occurrence | 0G760300 through 0T408999; 2:1 gear ratio catalog | 821354A2 |
| Mercury | 30 Jet | 30 | Not specified in occurrence | 0G590000 through 0G760299; 1.83:1 gear ratio catalog | 821354A2 |
| Mercury | 40, 2-cylinder | 40 | Not specified in occurrence | 0G055314 through 0G760299; 2.00:1 gear ratio catalog | 821354A2 |
| Mercury | 40, 3-cylinder | 40 | Not specified in occurrence | 0G760300 through 0T979999; 2.00:1 gear ratio catalog | 821354A2 |
| Mercury | 40, 4-Stroke | 40 | 4-Stroke | 0G231123 through 0G760299; 1.83:1/2:1 gear ratio catalog | 821354A2 |
| Mercury | 40, 4-Stroke | 40 | 4-Stroke | 0G760300 through 0T408999; 2:1 gear ratio catalog | 821354A2 |
| Mercury | 45 Bodensee | 45 | 4-Stroke | 0G231123 through 0G760299; 1.83:1/2:1 gear ratio catalog | 821354A2 |
| Mercury | 45 Bodensee | 45 | 4-Stroke | 0G760300 through 0T178499; non-Bigfoot 1.83:1 gear ratio catalog | 821354A2 |
| Mercury | 50, 3-cylinder | 50 | Not specified in occurrence | 0G590000 through 0G760299; 1.83:1 gear ratio catalog | 821354A2 |
| Mercury | 50, 3-cylinder | 50 | Not specified in occurrence | 0G760300 through 0T979999; 1.83:1 gear ratio catalog | 821354A2 |
| Mercury | 50 BigFoot | 50 | 4-Stroke | 0G231123 through 0G760299; 1.83:1/2:1 gear ratio catalog | 821354A2 |
| Mercury | 50 BigFoot | 50 | 4-Stroke | 0G760300 through 0T178499; non-Bigfoot catalog condition listed in source | 821354A2 |
Important: The available catalog evidence does not establish universal fitment for every Mercury 25–50 HP engine, nor does it independently confirm the previously listed Force applications. Check the complete model designation, serial number, gear ratio, and original water pump components before purchase.
Technical Specifications
- Product type
- Aftermarket water pump impeller repair kit
- Installation location
- Lower unit / gearcase water pump assembly
- Primary reference
- Mercury Marine 821354A2
- Kit configuration
- Impeller, gaskets, seals, wear plate, washer, and drive key as listed below
- Materials
- Neoprene impeller, stainless-steel wear plate, nylon tube components, and non-asbestos gasket material as supplied for this listing
- Dimensions
- Approximately 152.4 mm × 114.3 mm × 49.0 mm (6.0 in × 4.5 in × 1.93 in), as supplied for this listing
- Weight
- Approximately 0.17 kg (0.39 lb), as supplied for this listing
What's in the Box
- 1 × Tube seal, 700-85180
- 1 × Tube seal, 700-85181
- 1 × Washer, 700-31175 / 12-86645
- 1 × Water pump impeller, 700-89640 / 47-85089
- 1 × Upper gasket, 700-37490 / 27-822189
- 1 × Wear plate, 700-12505 / 8213542
- 1 × Lower gasket, 700-37700 / 27-822217
- 1 × Drive key, 85119
Component references are provided to help compare the kit with the parts removed from your engine. Confirm physical dimensions and component shape before installation.
Installation Notes
- Disconnect the battery and ignition system and follow the engine manufacturer's safety procedures.
- Drain the gearcase lubricant into a suitable container if required for lower-unit removal.
- Remove the lower unit from the driveshaft housing, taking care to maintain correct shift-shaft and water-tube alignment.
- Remove the water pump housing and retain the fasteners for inspection.
- Remove the old impeller, drive key, gaskets, seals, and wear plate.
- Clean the housing and mating surfaces thoroughly. Remove old gasket material and debris without damaging sealing surfaces.
- Install the replacement wear plate, gaskets, seals, drive key, and impeller in the correct order for your engine.
- Rotate the driveshaft in the correct direction while seating the impeller vanes in the housing; follow the service manual for your exact engine.
- Reinstall the water pump housing and tighten fasteners to the manufacturer's specifications.
- Reinstall the lower unit, ensuring the driveshaft, shift shaft, and water tube are correctly engaged.
- Refill the gearcase with the specified marine gear lubricant.
- Run and test the engine safely, confirming normal cooling-water flow and checking for leaks or overheating.
Troubleshooting and FAQ
How do I confirm that this kit fits my engine?
Match the complete engine model, horsepower, stroke, gear ratio, and serial number with the compatibility information. Also compare the old impeller, wear plate, gaskets, seals, and drive key with the components shown in the kit list. If any critical detail differs, consult the applicable service manual or a qualified marine technician before ordering.
What are common signs of a worn water pump impeller?
Typical signs include overheating at idle or low speed, weak or intermittent water flow from the telltale, reduced cooling performance, or damaged impeller vanes. Inspect the cooling system promptly if overheating occurs.
How often should the impeller be replaced?
Replacement intervals depend on the engine manufacturer's maintenance schedule and operating conditions. Regular inspection is especially important after extended storage or operation in saltwater, sand, or silt. Replace the impeller whenever the vanes are cracked, permanently set, torn, or otherwise damaged.
Why does the kit include two tube seals?
The listed kit configuration includes two tube-seal references for the covered water-pump variations. Compare both seals with the original parts and use only the seal that matches the application and location specified by the service information for your engine.
Is this an OEM Mercury part?
No. This is an aftermarket replacement kit associated with Mercury reference 821354A2. Mercury and Quicksilver are trademarks of their respective owners, and this product is not manufactured or sponsored by Mercury Marine.
Can I install the kit without removing the lower unit?
Water-pump service normally requires access to the lower-unit water pump housing. The exact procedure varies by engine. Use the service manual for your model and serial number, and seek professional assistance if you are not familiar with outboard lower-unit service.
Safety and Important Information
- Verify the engine model, serial number, gear ratio, and original parts before ordering.
- Do not operate an outboard that overheats or has weak cooling-water flow.
- Use the manufacturer's torque values, lubricant specification, and installation procedure for your exact engine.
- Professional installation is recommended when lower-unit removal or shift-shaft alignment is required.
- This product is an aftermarket replacement and is not an OEM component.
About Sea Sierra
- Marine replacement parts — Practical aftermarket components for routine service and repair.
- Application-focused listings — Product information is organized around engine model, serial, and component details.
- Value-oriented maintenance — Replacement kits help support scheduled water-pump service when the application is correctly verified.
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