Water Pump Impeller Kit – Fits Yamaha 25/30/40/50 HP (Replaces 6H4-44352, 6H4-W0078-00)

Water Pump Impeller Kit – Fits Yamaha 25/30/40/50 HP (Replaces 6H4-44352, 6H4-W0078-00)

This water pump impeller is designed for a precise fit on a range of Yamaha 2-stroke and 4-stroke outboard motors. It is compatible with 2-stroke 25-50 HP models manufactured from 1984-2002 and 4-stroke F20-F40 models from 1998-2011.

This component is a direct replacement for multiple Yamaha and aftermarket part numbers, ensuring reliable performance and compatibility for routine maintenance or repairs.

• Installation Method: Direct OEM replacement
• Included Parts: 1 x Water Pump Impeller
• Materials: Features a durable, marine-grade rubber impeller designed for longevity.

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 Yamaha owners, here’s a guide to help you identify your engine’s serial/model: Yamaha Serial Number Guide. You can also review exploded diagrams to verify part numbers: Yamaha Parts Diagrams & Catalog.

Yamaha 2-Stroke Models

Yamaha 4-Stroke Models

Technical Specifications

Package Contents

• 1 x Water Pump Impeller (6H4-44352-02)

Note: This is for the impeller only. For the complete water pump repair kit with housing and other components, please look for Yamaha part number 6H4-W0078-00.

Explosion Diagram

Installation Guide

1. Safety First: Disconnect the battery and ensure the engine is securely mounted before beginning work.
2. Access the Lower Unit: Drain the gearcase oil. Remove the bolts securing the lower unit (gearcase) to the upper casing and carefully lower it.
3. Open the Water Pump Housing: Locate the water pump assembly on top of the lower unit. Remove the bolts to lift the housing cover.
4. Inspect and Remove Old Impeller: Take note of the direction the old impeller vanes are facing. Remove the old impeller, key, gaskets, and wear plate.
5. Install New Impeller: Clean the housing interior. Install the new wear plate and key. Slide the new impeller into place, turning the driveshaft clockwise to bend the vanes in the correct direction.
6. Reassemble: Install the new gasket and re-bolt the housing cover to the specified torque.
7. Reattach Lower Unit: Realign the lower unit, ensuring the driveshaft, shift shaft, and water tube are correctly positioned. Bolt it back into place and refill the gearcase oil.
8. Test Operation: Reconnect the battery. Start the engine in a test tank or with a water flusher to confirm water is being discharged from the tell-tale port.

Troubleshooting & FAQ

How do I confirm this impeller fits my engine?
The most reliable method is to match your engine's model and year against the compatibility tables above. You can also use the OEM part number from your engine's service manual and check it against our cross-reference list. For Yamaha owners, our Yamaha Serial Number Guide can help you identify your model.

What are the signs of a failing water pump impeller?
Common signs include a weak or nonexistent water stream from the engine's tell-tale port, frequent engine overheating alarms, and a dry, cracked, or brittle appearance on the old impeller upon inspection.

How often should I replace the water pump impeller?
For preventative maintenance, it is recommended to inspect the impeller annually and replace it every 1-2 years, or after every 100-200 hours of use, depending on operating conditions (e.g., saltwater vs. freshwater). Running the pump dry, even for a few seconds, can cause immediate damage.

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.