Water Pump Repair Kit – Fits Mercury/Mariner 25-50HP Outboards (Replaces 821354A2)

Water Pump Repair Kit – Fits Mercury/Mariner 25-50HP Outboards (Replaces 821354A2)

This water pump repair kit provides all the necessary components to restore the cooling system on a wide range of Mercury/Mariner and Force outboard engines. It is designed to fit 25-50HP, 2-stroke & 4-stroke Mercury/Mariner engines from 1994–2018 and 40-50HP, 2-stroke Force engines from 1995–1997.

This assembly is a direct replacement for Mercury OEM part numbers 821354A2, 821354A1, and 821354A04, ensuring a precise fit and reliable performance. It is also cross-compatible with several aftermarket kits.

• Engineered as a direct OEM-quality replacement for a guaranteed fit.
• Includes a durable neoprene impeller and a 316 stainless steel wear plate for corrosion resistance.
• The kit contains all required gaskets, seals, and hardware for a complete overhaul.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Mercury owners, here’s a guide to help you identify your engine’s serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Mercury/Mariner Outboard Applications

Force Outboard Applications

Technical Specifications

Package Contents

• 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 Guide

1. Safety First: Disconnect the battery and remove the spark plug leads.
2. Remove Lower Unit: Shift the outboard into neutral. Unbolt and carefully lower the gearcase (lower unit) from the engine leg.
3. Access the Pump: Locate the water pump housing on top of the lower unit. Remove the bolts securing the housing.
4. Disassemble Old Pump: Lift off the housing. You may need to gently pry it. Remove the old impeller, wear plate, and gaskets. Note the orientation of the impeller vanes.
5. Clean and Prepare: Thoroughly clean all mating surfaces, removing any old gasket material or sealant residue.
6. Install New Components: Place the new lower gasket and stainless steel wear plate onto the gearcase.
7. Install Impeller: Insert the new impeller key into the driveshaft. Slide the new impeller onto the shaft, turning it clockwise to bend the vanes correctly.
8. Install Housing: Apply a thin layer of marine grease to the inside of the new housing. Place the new upper gasket and install the housing over the impeller.
9. Secure and Reassemble: Fasten the housing with the original bolts, tightening them to the manufacturer's specified torque.
10. Reinstall Lower Unit: Carefully guide the lower unit back into place, ensuring the driveshaft, shift shaft, and water tube align properly. Secure it with the mounting bolts.
11. Final Checks: Reconnect the spark plug leads and battery.
12. Test Operation: Start the engine in a test tank or with a flusher attached. Confirm a steady stream of water is exiting the tell-tale port.

Troubleshooting & FAQ

How do I confirm this kit fits my Mercury engine?

This kit fits a wide range of Mercury/Mariner 25-50HP models from 1994–2018 and Force 40-50HP models from 1995–1997. Please check the "Compatible Engine Models" table and use your engine's serial number to confirm. For Mercury owners, our Serial Number Guide can help you find your number.

What are the signs that my water pump needs to be replaced?

Common signs of a failing water pump include the engine overheating, a weak or non-existent water stream from the "telltale" outlet, and visible damage such as cracks or brittleness of the old impeller upon inspection.

How often should I replace my water pump impeller?

For preventative maintenance, it is recommended to inspect and replace your water pump impeller every 1-2 years or every 100-200 hours of operation. Service intervals can vary based on usage conditions (e.g., saltwater vs. freshwater, high-debris environments).

OEM vs. Aftermarket?

This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

How fast do you ship and how much does it cost?

We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

What is your warranty and return policy?

This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.