Water Pump Repair Kit – Fits Yamaha 25/30 HP Outboard Motors (Replaces 6J8-W0078-A2-00)

Water Pump Repair Kit – Fits Yamaha 25/30 HP Outboard Motors

This water pump repair kit provides the necessary components to service and restore the water pump on select Yamaha 2-stroke outboard motors. It is designed to fit Yamaha 25 HP models from 1999 and 2001–2002, and 30 HP models from 1997–1999 and 2001–2002.

The kit serves as a direct replacement for multiple OEM and aftermarket part numbers, including Yamaha 6J8-W0078-A2-00, 6J8-W0078-A1-00, 6J8-W0078-C2-00, Mercury 879136, Sierra 18-3430, and GLM 12285/12284.

• Installation Location: Mounts in the lower unit of the outboard motor.
• Fitment: Engineered as a direct-fit replacement for the original components.
• Complete Kit: Includes a new impeller, gaskets, cartridge, plate, and bolts required for a standard rebuild.

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.

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 Cartridge Insert (663-44322-00-00)
• 1 x Impeller (6H4-44352-02-00)
• 1 x Water Pump Gasket (663-44315-A0-00)
• 1 x Outer Plate, Cartridge (663-44323-00-00)
• 1 x Gasket, Cartridge (663-44324-A0-00)
• 1 x Water Pump Gasket (663-44316-A0-00)
• 2 x Bolt, With Washer (90119-08M13-00)
• 2 x Bolt, With Washer (90119-08M34-00)

Installation Guide

1. Disconnect the negative battery cable and remove the propeller.
2. Place a drain pan under the lower unit and remove the gearcase lubricant drain screw.
3. Unbolt and carefully slide the lower unit off the outboard's driveshaft housing.
4. Remove the bolts securing the water pump housing and lift it off to expose the impeller.
5. Remove the old impeller, plate, and gaskets. Note the orientation of the impeller vanes.
6. Thoroughly clean all mating surfaces, removing any old gasket material or sealant.
7. Install the new cartridge insert, gaskets, and plate.
8. Slide the new impeller onto the driveshaft, rotating clockwise to bend the vanes correctly.
9. Reinstall the water pump housing and tighten the bolts to the manufacturer's specified torque.
10. Reattach the lower unit, refill with fresh gearcase lubricant, and reinstall the propeller.
11. Reconnect the battery and test the engine in water to confirm proper water circulation from the tell-tale outlet.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my specific engine?

A: Start by checking your engine's model and year against the "Compatible Engine Models" table. You can also compare your existing part numbers with those in the "Part Number Cross-Reference" section. For detailed verification, please use the Yamaha and Mercury serial number guides linked above.

Q: What are the common symptoms of a bad water pump?

A: Key indicators of a failing water pump include the engine overheating, an alarm sounding, or a weak, inconsistent, or non-existent water stream from the "tell-tale" outlet on the side of the motor.

Q: How often should I replace my water pump impeller?

A: For preventative maintenance, it is highly recommended to inspect the impeller annually and replace it every 1 to 2 years (or every 100-200 hours of operation), particularly if you operate in saltwater or silty/sandy conditions.

Q: Does this kit include the water pump housing?

A: No, this kit is designed to rebuild the internal wear components of your existing water pump assembly. The metal housing is not included, as noted in the Technical Specifications.

Q: Is this an OEM or aftermarket part?

A: 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.

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

A: 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.

Q: What is your warranty and return policy?

A: 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.