Water Pump Impeller Repair Kit – Fits Yamaha 2-Stroke 40, 50 HP & 4-Stroke 40, 50, 60 HP (Replaces 63D-W0078-01-00, Sierra 18-3434)

Water Pump Impeller Repair Kit – Fits Yamaha 2-Stroke & 4-Stroke Engines

This water pump impeller repair kit provides all the necessary components for servicing and rebuilding the water pump on a wide range of Yamaha outboards. It is designed to restore the performance and reliability of your engine's cooling system.

This kit is a direct replacement for Yamaha outboards, fitting specific 2-Stroke 40 and 50 HP models (1995–2005) and 4-Stroke 40, 50, and 60 HP models (1995–2009). It directly corresponds to OEM part number 63D-W0078-01-00.

• Engine Compatibility: Fits select Yamaha 2-Stroke (40, 50 HP) and 4-Stroke (40, 50, 60 HP) outboards.
• Installation Type: Direct replacement for OEM components.
• Kit Contents: Complete kit for a full water pump service, including impeller, housing cover, gaskets, and hardware.

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 Outboards

Yamaha 4-Stroke Outboards

Technical Specifications

Package Contents

• 1 x Impeller (6H3-44352-00-00)
• 1 x Cartridge Insert (63D-44322-00-00)
• 1 x Pump Housing Cover (63D-44312-00-00)
• 1 x Cartridge Outer Plate (63D-44323-00-00)
• 1 x O-Ring (93210-59MG7-00)
• 1 x Water Pump Gasket (63D-44316-00-00)
• 4 x Bolt, with Washer (90119-08M15-00)
• 1 x Water Seal Damper 2 (663-44366-00-00)
• 1 x Woodruff Key (90280-03024-00)

Installation Guide

1. Disconnect the battery and shift the outboard into neutral.
2. Remove the lower unit (gearcase) by unbolting it from the engine's midsection.
3. Locate the water pump housing, typically situated on top of the gearcase.
4. Unbolt and remove the old pump housing cover and components. Note their orientation.
5. Clean all mating surfaces thoroughly, removing old gasket material and debris.
6. Install the new gasket, plates, impeller, and key from the kit. Ensure the impeller vanes are oriented correctly (typically clockwise).
7. Install the new cartridge insert and O-ring.
8. Fasten the new pump housing cover, tightening bolts to the manufacturer's specified torque.
9. Reinstall the lower unit, ensuring the driveshaft and water tube align correctly.
10. Reconnect the battery and test the engine using a water supply (flushing muffs) to verify proper cooling.

Troubleshooting & FAQ

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

A: The best way to ensure fitment is to check your engine's model and year against the compatibility tables above. We also recommend using the Yamaha Serial Number Guide linked above to verify your details precisely.

A: This kit (18-3434) contains all the core components for a water pump rebuild, including the impeller, wear plate, and gaskets. It does not include the main water pump housing. The Sierra 18-3415 kit is a larger assembly that typically includes the housing itself.

A: Common signs include the engine overheating at idle or low speeds, and a weak or nonexistent stream of water from the "tell-tale" outlet. Visible damage to the old impeller, such as cracked or missing vanes, also indicates it's time for a replacement.

A: As a general rule, impellers should be inspected annually and replaced every 1-2 years or every 100-200 hours of use, whichever comes first. This interval can be shorter if you operate in saltwater or sandy/silty conditions.

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.

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.

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.