Water Pump Impeller Kit for Mercury, Mariner & Force Outboards – 25–50 HP – Replaces 821354A1, 821354A2 & 821354A04
Water Pump Impeller Kit for Mercury, Mariner & Force Outboards – 25–50 HP – Replaces 821354A1, 821354A2 & 821354A04 is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
U.S. orders usually arrive within 6–15 days, depending on stock location and destination.
International delivery times may vary due to customs processing.
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Water Pump Impeller Kit for Mercury, Mariner & Force Outboards ...
Water Pump Impeller Kit for Mercury, Mariner & Force Outboards – 25–50 HP – Replaces 821354A1, 821354A2 & 821354A04 is backordered and will ship as soon as it is back in stock.
Product Details
This water pump impeller kit is designed for servicing the cooling system on selected Mercury and Mariner 25–50 HP outboards and Force 40–50 HP outboards. The kit contains the primary wear components needed for a standard water-pump service and can help restore proper cooling-water flow when an impeller is worn, cracked, brittle, or damaged.
It is listed as a replacement for Mercury part numbers 821354A1, 821354A2, and 821354A04, with aftermarket reference numbers including Sierra 18-4531 and GLM 12045. Always compare the original component, engine model, horsepower, year, and serial number before ordering.
- Installs in the lower unit of the outboard motor.
- Suitable for fresh- and saltwater service when installed and maintained correctly.
- Includes a neoprene impeller, stainless-steel wear plate, gaskets, seals, washer set, and drive key.
- The water-pump housing is not included.
Part Number Matrix
Use the following references to compare the listed OEM and aftermarket numbers. These numbers should be confirmed against the engine model and serial-number range before installation.
| Brand | Part Number | Superseded By | Notes |
|---|---|---|---|
| Mercury | 821354A1 | 821354A2 | Replacement reference |
| Mercury | 821354A04 | 821354A2 | Replacement reference |
| Mercury | 821354A2 | OEM reference | |
| Sierra | 18-4531 | Aftermarket interchange reference | |
| GLM | 12045 | Aftermarket interchange reference |
Engine & Model Compatibility
The compatibility information below is provided as a reference for selected applications. Confirm the complete model designation and serial-number range before purchase, because horsepower and year alone may not establish an exact fit.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 25 HP | 25 | 4-Stroke | 1998–Up | 821354A1/A2 | Carbureted; 0G590000–0T408999 |
| Mercury | 30 HP | 30 | 4-Stroke | 1998–Up | 821354A1/A2 | Carbureted; 0G760300–0T408999 |
| Mercury | 30 HP | 30 | 4-Stroke | 1998–Up | 821354A1/A2 | Jet; 0G590000 and later |
| Mercury | 30 HP | 30 | 2-Stroke | 1994–2007 | 821354A1/A2 | 2-cylinder; 0G053314 and later |
| Mercury | 40 HP | 40 | 2-Stroke | 1994–2007 | 821354A1/A2 | 2-cylinder; 0G053314 and later |
| 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-cylinder; 0G531301 and later |
| Mercury | 45 HP | 45 | 4-Stroke | 1995–2000 | 821354A1/A2 | Bodensee; 0G231123 and later |
| Mercury | 50 HP | 50 | 2-Stroke | 1998–Up | 821354A1/A2 | 3-cylinder; 0G590000 and later |
| Mercury | 50 HP | 50 | 4-Stroke | 1995–2008 | 821354A1/A2 | 0G231123 and later |
| 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 Specifications
- Product Type
- Water pump impeller kit
- Installation Location
- Lower unit
- Wear Plate Material
- Stainless steel
- Component Materials
- Neoprene impeller, nylon PA66 tube, and non-asbestos gaskets
- Weight
- 150 g (5.3 oz)
- Compatible Environment
- Freshwater and saltwater use
- Product Classification
- Aftermarket replacement kit
What’s in the Box
- 1 × Water pump impeller (47-85089-10)
- 1 × Drive key (85119)
- 1 × Wear plate (8213542)
- 1 × Upper gasket (27-822189)
- 1 × Lower gasket (27-822217)
- 1 × Short tube seal (43023)
- 1 × Long tube seal (823547-1)
- 2 × Washers (12-86645)
Installation Notes
- Disconnect the battery and place the outboard in neutral before beginning work.
- Place a drain pan beneath the lower unit and remove the drain and fill screws to drain the gearcase lubricant.
- Remove the bolts securing the lower unit to the upper driveshaft housing.
- Carefully lower and separate the gearcase assembly from the outboard.
- Remove the water-pump housing cover to access the impeller. Note the direction of the existing impeller vanes.
- Remove the old impeller, drive key, wear plate, gaskets, and seals. Clean all mating surfaces thoroughly.
- Install the supplied wear plate, gaskets, and seals in the correct order.
- Apply a light coat of suitable grease to the driveshaft. Install the new drive key and slide the impeller into position while turning the shaft in the correct direction so the vanes are oriented properly.
- Reinstall the water-pump housing and make sure all seals are seated correctly. Tighten the housing bolts to the engine manufacturer’s specifications.
- Guide the gearcase back into position, aligning the driveshaft, shift shaft, and water tube. Tighten the retaining bolts to specification.
- Refill the gearcase with the correct type and quantity of marine lubricant.
- Reconnect the battery. Using an appropriate water supply or flushing muffs, run the engine and confirm a steady stream from the tell-tale outlet.
Troubleshooting & FAQ
How can I confirm that this impeller kit fits my engine?
Compare your engine brand, model, horsepower, year, stroke, and serial number with the compatibility information above. Also compare the original impeller, wear plate, and gasket arrangement. If any detail differs, verify the application before installation.
What are common signs that a water-pump impeller needs replacement?
Typical signs include engine overheating, especially at idle or low speed; a weak or intermittent tell-tale stream; and an impeller with cracked, brittle, deformed, or missing vanes.
How often should the water-pump impeller be replaced?
Impeller service intervals depend on engine use and manufacturer recommendations. Preventive replacement is commonly performed at regular annual service, with more frequent inspection when operating in sandy, silty, or debris-filled water.
Does this kit include the complete water-pump housing?
No. This is an impeller service kit. It includes the listed impeller, drive key, wear plate, gaskets, seals, and washers. The main water-pump housing is not included and should be inspected separately for wear, scoring, or cracks.
Is this an OEM part?
No. This is an aftermarket replacement kit. The OEM and aftermarket numbers shown on this page are reference numbers used to help compare applications and should not be interpreted as an OEM-manufacturer claim.
What are the shipping speeds and costs?
Typical transit time is 5–15 days for most regions. Standard shipping is free on qualifying orders. Expedited options, where available for your location, are displayed at checkout.
What is the warranty and return policy?
This product is covered by a 1-year warranty against manufacturing defects under normal use conditions. Returns are accepted for unused items in their original packaging within the applicable return window. Contact customer support for current policy details and return instructions.
Safety & Important Information
- Confirm the engine model, serial number, original part, and component dimensions before purchase. Do not install the kit if the parts do not match your application.
- This is an aftermarket replacement component. Brand names and part numbers are used for identification and reference only.
- Follow the engine manufacturer’s service procedures, torque specifications, lubricant requirements, and safety instructions.
- Professional installation is recommended. Incorrect water-pump installation can cause insufficient cooling and serious engine damage.
- After installation, verify proper water flow and monitor the engine for overheating before returning it to regular service.
About Sea Sierra
- Pro-Grade Standards — We supply marine replacement parts selected for practical fit, function, durability, and serviceability.
- Fast Global Fulfillment — We offer standard delivery to most regions, with typical transit times of 5–15 days.
- Manufacturer-Direct Value — We aim to provide dependable replacement parts at competitive prices while maintaining consistent product information and support.
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