Water Pump Impeller Kit – Fits Johnson/Evinrude 4, 4.5, 5, 6, 8 HP (Replaces 396644, 389844)

Water Pump Impeller Kit – Fits Johnson/Evinrude 4, 4.5, 5, 6, 8 HP (Replaces 396644, 389844)

This water pump impeller repair kit provides a complete solution for servicing the cooling system on a wide range of Johnson and Evinrude outboard motors. It is designed to fit various 2-stroke and 4-stroke models from 4 HP to 8 HP manufactured over several decades.

This kit serves as a direct replacement for Johnson/Evinrude part numbers 396644, 389844, and 765603, as well as Sierra part number 18-4529.

• Includes all necessary components for a standard water pump rebuild: impeller, housing, plate, gaskets, and hardware.
• Engineered as a direct OEM replacement for straightforward installation.
• Restores cooling performance to prevent engine overheating and ensure reliability.

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 Johnson/Evinrude owners, here’s a guide to help you identify your engine’s serial/model: Johnson/Evinrude Serial Number Guide.

Technical Specifications

Package Contents

• 1 x Impeller Assembly (389576, 18-3091)
• 1 x Impeller Housing Plate (324640, 18-4578)
• 1 x Impeller Housing Cup (324641, 18-4551)
• 1 x Impeller Housing Gasket (325040, 18-99156)
• 1 x Drive Key (331130, 18-3026)
• 1 x Grommet (321129, 18-1827)
• 1 x Grommet (302497, 18-3329)
• 1 x Screws (324430, 18-4277)
• 1 x O-Ring (303191, 18-7413)
• 1 x Gasket (311598) - Note: included in some kits, may vary.

Installation Guide

1. Safety First: Disconnect the battery and shift the outboard into neutral.
2. Access the Pump: Unbolt and carefully remove the lower unit (gearcase) from the outboard's midsection. You may need to disconnect a speedometer tube.
3. Disassemble Housing: Remove the bolts securing the water pump housing cover to access the impeller.
4. Remove Old Components: Note the rotational direction of the old impeller's vanes before removing it. Take out the old gaskets, wear plate, and drive key.
5. Clean Surfaces: Thoroughly clean all mating surfaces, ensuring no old gasket material, sealant, or corrosion remains.
6. Install New Parts: Place the new gasket and wear plate onto the gearcase. Slide the new drive key onto the driveshaft.
7. Insert New Impeller: Lubricate the new impeller and housing interior with a marine-safe lubricant. Install the impeller by pushing down while turning the driveshaft clockwise to bend the vanes correctly.
8. Reassemble Housing: Install the new housing cup and gasket, then secure the housing cover with the provided screws, tightening them to the manufacturer's specified torque.
9. Reinstall Lower Unit: Carefully guide the lower unit back into place, ensuring the driveshaft, shift shaft, and water tube align correctly. Bolt it securely.
10. Test Operation: Reconnect the battery. Start the engine in water and immediately verify a strong, steady stream of water is exiting the tell-tale port.

Troubleshooting & FAQ

How do I confirm this kit fits my engine?

First, check the "Compatible Engine Models" table above and match your engine's horsepower, stroke, and model year. For Johnson/Evinrude owners, our serial number guide can help you verify your model details.

What are the signs my water pump impeller needs replacement?

Common signs of a failing impeller include a weak or intermittent water stream from the engine's tell-tale outlet, the engine overheating alarm sounding, or steam from the exhaust. Proactive replacement is recommended to avoid engine damage.

How often should I replace the water pump impeller?

As a general maintenance rule, it is best practice to inspect your impeller annually and replace it every 1-2 years or every 100-200 hours of use. Replacement frequency should be increased if you operate 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.