Water Pump Impeller Kit – Fits Mercury Marine 25-50 HP (Replaces 821354A2, 821354A1)

Water Pump Impeller Kit – Fits Mercury Marine 25-50 HP (Replaces 821354A2, 821354A1)

This water pump impeller repair kit is designed for Mercury Marine 25-50 HP 4-Stroke outboards (1998–Up), including 25, 30, 40, 45, and 50 HP models. It also fits select Force 40/50 HP outboards from 1995–1997.

This kit serves as a direct replacement for Mercury/Quicksilver part numbers 821354A1, 821354A2, and 821354A04, as well as aftermarket parts from Sierra, GLM, and Recmar.

• Engineered with a durable neoprene impeller for reliable performance.
• Includes all necessary gaskets, seals, and a stainless steel wear plate for a complete overhaul.
• Installs in the lower unit (gearcase) to restore cooling system efficiency.

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 Tube Seal (700-85180)
• 1 x Tube Seal (700-85181)
• 1 x Washer (700-31175/12-86645)
• 1 x Water Pump Impeller (700-89640/47-85089)
• 1 x Gasket Upper (700-37490/27-822189)
• 1 x Wear Plate (700-12505/8213542)
• 1 x Gasket Lower (700-37700/27-822217)
• 1 x Drive Key (85119)

Installation Guide

1. Disconnect the negative battery cable for safety.
2. Place the outboard motor in the neutral gear position.
3. Carefully unbolt and remove the lower unit (gearcase) from the engine's driveshaft housing.
4. Unscrew the bolts securing the water pump housing and remove the housing.
5. Take note of the old impeller's vane direction before removing it, along with the old wear plate and gaskets.
6. Thoroughly clean all contact surfaces, removing any old gasket material or debris.
7. Install the new lower gasket, stainless steel wear plate, and drive key.
8. Slide the new impeller onto the driveshaft, rotating it in the direction of engine operation to correctly bend the vanes.
9. Place the new upper gasket on the housing and reinstall the water pump housing, ensuring a snug fit.
10. Carefully guide the lower unit back into position, aligning the driveshaft, shift shaft, and water tube.
11. Secure the lower unit by fastening all bolts to the manufacturer's recommended torque.
12. Reconnect the battery, start the engine in a water source, and confirm a steady stream from the tell-tale outlet.

Troubleshooting & FAQ

How do I confirm this fits my engine?
To ensure compatibility, check your engine's serial number against the ranges listed in the "Compatible Engine Models" table above. For Mercury owners, our Mercury Serial Number Guide can help you locate this number and verify the fit.

What are the signs of a failing water pump impeller?
Common signs include the engine overheating at idle or low speeds, a weak or inconsistent water stream from the "tell-tale" cooling outlet, or a complete lack of water flow. Upon inspection, the old impeller may have cracked, brittle, or worn-down rubber vanes.

How often should I replace the impeller?
For preventative maintenance and to ensure engine reliability, it is recommended to replace the water pump impeller every 1 to 2 years or after every 100-200 hours of use. Replacement frequency should be increased if operating in sandy, silty, or saltwater conditions.

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.