Water Pump Repair Kit – Fits Mercury/Mariner 25-50 HP Outboards (Replaces 821354A2, 821354A1, 821354A04)

Water Pump Repair Kit – Fits Mercury/Mariner 25-50 HP Outboards (Replaces 821354A2, 821354A1, 821354A04)

This water pump repair kit provides the necessary components to service and restore the cooling system on select Mercury, Mariner, and Force outboard engines. It is designed to fit 25-50 HP 2-stroke and 4-stroke outboards from 1995–2018 and 40-50 HP Force outboards from 1995–1999.

This kit is a direct replacement for Mercury Marine part numbers 821354A2, 821354A1, and 821354A04. It also serves as an aftermarket cross-reference for Sierra 18-4531, GLM 12045, and SEI Marine 96-265-03BK.

• Engineered for installation in the lower unit (gearcase).
• Constructed with a corrosion-resistant metal alloy housing and a high-performance neoprene rubber impeller for durability.
• Includes all essential gaskets, seals, and hardware for a complete water pump 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.

Technical Specifications

Package Contents

• 1 x Water Pump Impeller (Replaces 47-85089-10, 47-85089-3)
• 1 x Drive Key
• 1 x Face Plate/Wear Plate (Replaces 821354-2)
• 1 x Upper Gasket (Replaces 27-822189)
• 1 x Lower Gasket (Replaces 27-822217)
• 1 x Short Water Tube Seal (Replaces 43023)
• 1 x Long Water Tube Seal (Replaces 823547-1)
• 2 x Washer (Replaces 12-86645-1)

Installation Guide

Professional installation is recommended. The following steps are a general guide:

1. Disconnect the battery and shift the outboard motor into the neutral position.
2. Place a drain pan under the lower unit and remove the drain/fill screws to drain the gearcase oil.
3. Remove the bolts that secure the lower unit (gearcase) to the engine's midsection.
4. Carefully separate the lower unit from the engine, taking care not to damage the driveshaft or shift rod.
5. Unbolt and remove the old water pump housing to expose the impeller and wear plate.
6. Remove the old impeller, drive key, gaskets, and seals from the driveshaft and housing.
7. Thoroughly clean all mating surfaces, ensuring complete removal of any old gasket material or corrosion.
8. Install the new lower gasket, wear plate, and drive key from the kit.
9. Slide the new impeller onto the driveshaft, rotating it clockwise to seat the vanes correctly within the housing.
10. Install the new upper gasket and any seals, then carefully position the housing and tighten the bolts to specification.
11. Re-install the lower unit onto the midsection, ensuring the driveshaft, shift rod, and water tube are correctly aligned.
12. Refill the gearcase with the correct type and amount of marine gear lube and reconnect the battery before starting the engine.

Troubleshooting & FAQ

How do I confirm this kit fits my specific engine model?
Check the "Compatible Engine Models" table on this page. Match your engine's brand, model, HP, and year/serial number range to the listed specifications. This kit is a direct replacement for Mercury OEM part numbers 821354A2, 821354A1, and 821354A04.

What are the signs that my water pump needs replacement?
Common signs of a failing water pump include a weak or nonexistent water stream from the "tell-tale" outlet, frequent engine overheating alarms, or discovering a brittle, cracked, or melted impeller during a routine inspection.

How often should I replace the water pump impeller?
For preventative maintenance, it's recommended to inspect the impeller annually and replace the entire water pump kit every 2-3 years or every 200-300 hours of use. Replacement intervals should be shorter if you frequently operate in saltwater or debris-heavy water.

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.