Water Pump Impeller Kit for Mercury/Mariner 25–50 HP Outboards – Replaces 821354A2
Water Pump Impeller Kit for Mercury/Mariner 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 Kit for Mercury/Mariner 25–50 HP Outboards – Re...
Water Pump Impeller Kit for Mercury/Mariner 25–50 HP Outboards – Replaces 821354A2 is backordered and will ship as soon as it is back in stock.
Product Details
This water pump impeller kit provides the service components needed to restore the cooling-water pump on compatible Mercury and Mariner outboard engines. It is listed for Mercury and Mariner 25–50 HP outboards, including applicable four-stroke models from 1998 onward, selected two-stroke models, and specific Force 40–50 HP two-stroke models from 1995–1997.
The kit is intended as an aftermarket replacement for applications using Mercury part references 821354A1, 821354A2, and 821354A04. Additional aftermarket reference numbers include Sierra 18-4531 and GLM 12045. Always confirm the engine model, horsepower, stroke, year, and serial-number range before ordering.
- Designed for installation in the lower-unit water-pump housing.
- Includes a neoprene-rubber impeller, stainless-steel wear plate, gaskets, seals, drive key, and washers.
- Supplies the primary service components for a water-pump replacement.
Part Number Matrix
Use the following references to compare the listed OEM and aftermarket numbers with the part being replaced.
| Brand | Part Number | Notes |
|---|---|---|
| Mercury | 821354A1 | Earlier listed reference |
| Mercury | 821354A2 | Primary replacement reference |
| Quicksilver | 821354A2 | Listed manufacturer reference |
| Mercury | 821354A04 | Later listed reference |
| Sierra | 18-4531 | Aftermarket reference |
| GLM | 12045 | Aftermarket reference |
Engine & Model Compatibility
Compatibility depends on the complete engine application, including model configuration and serial-number range. Confirm the details below against the engine identification label and the original water-pump parts before installation.
| Brand | Model | Rated HP | Stroke | Years | Reference | Serial or Application Notes |
|---|---|---|---|---|---|---|
| Mercury | 25 HP Four Stroke Carb | 25 | 4-Stroke | 1998 onward | 821354A2 | 0G590000–0T408999 |
| Mercury | 30 HP Four Stroke Carb | 30 | 4-Stroke | 1998 onward | 821354A2 | 0G760300–0T408999 |
| Mercury | 30 HP Jet | 30 | 4-Stroke | 1998 onward | 821354A2 | 0G590000 onward |
| Mercury | 30/40 HP, 2-cylinder | 30–40 | 2-Stroke | 1998 onward | 821354A2 | 0G053314 onward |
| Mercury | 40 HP, 3-cylinder | 40 | 2-Stroke | 1998 onward | 821354A2 | 0G531301 onward |
| Mercury | 40/45 HP Four Stroke 2:1 | 40–45 | 4-Stroke | 1998 onward | 821354A2 | 0G760300–0T408999 |
| Mercury | 45 HP Four Stroke Bodensee | 45 | 4-Stroke | 1998 onward | 821354A2 | 0G231123 onward |
| Mercury | 50 HP, 3-cylinder | 50 | 2-Stroke | 1998 onward | 821354A2 | 0G590000 onward |
| Mercury | 50 HP Four Stroke | 50 | 4-Stroke | 1998 onward | 821354A2 | 0G231123 onward |
| Mercury | 50 HP BigFoot | 50 | 4-Stroke | 1998 onward | 821354A2 | Confirm the complete model and serial number |
| Mariner | 25–50 HP models | 25–50 | 4-Stroke | 1998 onward | 821354A2 | Confirm the complete model and serial number |
| Force | 40 HP outboard | 40 | 2-Stroke | 1995–1997 | 821354A2 | 0E093700–0E287999 |
| Force | 50 HP outboard | 50 | 2-Stroke | 1995–1997 | 821354A2 | 0E093700–0E287999 |
Technical Specifications
- Product Type
- Water pump impeller kit
- Installation Location
- Engine lower unit and water-pump housing
- Drive Type
- Direct drive
- Materials
- Neoprene-rubber impeller, stainless-steel wear plate, and nylon PA66 tube
- Color
- Silver and black components
- Weight
- 0.15 kg (5.3 oz)
- Fitment Type
- Direct fit to the listed water-pump housing applications
What’s in the Box
- 1 × Water pump impeller — references 47-85089, 8508910, 850893, 8M0027792, and 8M0024502
- 1 × Impeller drive key — reference 85119
- 1 × Wear plate — reference 8213542
- 1 × Upper gasket — reference 27-822189
- 1 × Lower gasket — reference 27-822217
- 1 × Short tube seal — reference 43023
- 1 × Long tube seal — references 8235471 and 823547-1
- 2 × Washer — reference 12-86645
Installation Notes
- Disconnect the battery, remove the engine cowling, and place the outboard in neutral.
- Place a drain pan below the lower unit and remove the gearcase oil drain and fill screws as required for service.
- Remove the fasteners connecting the lower unit to the driveshaft housing, then carefully separate the lower unit.
- Remove the water-pump housing fasteners from the top of the gearcase.
- Lift the housing from the driveshaft and note the direction of the existing impeller vanes.
- Remove the old impeller, drive key, gaskets, seals, and wear plate. Clean the mating surfaces.
- Install the new wear plate, gaskets, drive key, seals, and impeller in the correct order. Orient the impeller vanes to match the direction required by the engine.
- Lubricate the inside of the housing with a suitable lubricant and use gasket sealant only where specified by the engine service instructions.
- Reinstall the water-pump housing and lower unit, making sure the driveshaft, shift shaft, and water tube align correctly.
- Refill the gearcase with the correct lubricant, reconnect the battery, and test the engine with an appropriate water supply. Check for a steady tell-tale stream and signs of leakage or overheating.
Troubleshooting & FAQ
How do I confirm whether this kit fits my engine?
Match the engine brand, model configuration, horsepower, stroke, year, and serial-number range with the compatibility information above. Compare the original impeller and water-pump components with the listed references before ordering.
What are common signs of a failing water-pump impeller?
Symptoms may include a weak or missing tell-tale stream, overheating warnings or alarms, steam near the exhaust, and reduced performance. Stop operation if the engine overheats and inspect the cooling system.
How often should an outboard impeller be replaced?
Replacement intervals vary by engine manufacturer, operating hours, storage conditions, and water quality. Inspect the impeller during scheduled maintenance and replace it when inspection or the service manual indicates.
What can cause premature impeller failure?
Common causes include running the engine without an adequate water supply, sand or silt entering the pump, prolonged storage, and age-related hardening or cracking of the rubber.
Is the drive key necessary?
Yes. The drive key locks the impeller to the driveshaft so the impeller rotates with the shaft and pumps cooling water. Install it correctly and verify that the impeller turns with the shaft.
Is this an OEM part?
No. This listing is for an aftermarket replacement kit. The listed OEM and aftermarket numbers are reference numbers for application checking and should not be interpreted as a claim that the kit is manufactured by Mercury, Mariner, Quicksilver, Sierra, or GLM.
How fast is shipping?
Shipping availability and delivery estimates depend on the destination and the service selected at checkout. The applicable options and estimated delivery date are shown during checkout.
What are the warranty and return terms?
Warranty coverage and return eligibility are governed by the applicable order and store policies. Contact support with the order details before returning or installing a part if you believe the item is incorrect or defective.
Safety & Important Information
- Verify the engine model, horsepower, stroke, year, and serial number before purchase.
- Compare the original part and water-pump housing with the listed references. Do not install a part that differs from the required application.
- This is an aftermarket replacement component, not an original-equipment manufacturer part.
- Follow the engine service manual and use appropriate safety procedures. Incorrect installation can cause loss of cooling and engine damage.
About Sea Sierra
- Marine Replacement Parts: We supply replacement components for marine maintenance and repair applications.
- Application-Focused Listings: Product references and compatibility information are provided to help customers compare parts before ordering.
- Customer Support: Contact support with your engine details and order information if you need help confirming an application.
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