SKU: 91825021372

Water Pump Repair Kit – Fits Yamaha 2-Stroke 40-50HP (Replaces 6H4-W0078-00-00, Sierra 18-3429)

Sale price$26.99 Regular price$29.99
Save 10%

Pay in installments of $7.50 with ShopPay, AfterPay and Klarna

Shipping Estimate
USA
  • USA
  • CAN

Ships within 48 hours · Estimated delivery Aug 13 - Aug 18

Promo Codes Available:

For Your Every Summer RSVP, with Code: SUMMER15

Description

Water Pump Repair Kit – Fits Yamaha 2-Stroke 40-50HP (Replaces 6H4-W0078-00-00, Sierra 18-3429)Water Pump Repair Kit Fits Yamaha 2 Stroke 40 50HP (Replaces 6H4 W0078 00 00, Sierra 18 3429) This water pump repair kit is designed for select Yamaha 2 stroke outboard engines, including 40HP (19841994), 50HP (19841987), Pro Series 50HP (19871990), and P50 models (19951996). It provides the necessary components to overhaul your engine's cooling system for reliable performance. This kit serves as a direct replacement for Yamaha part numbers 6H4 W0078

Water Pump Repair Kit – Fits Yamaha 2-Stroke 40-50HP (Replaces 6H4-W0078-00-00, Sierra 18-3429)

This water pump repair kit is designed for select Yamaha 2-stroke outboard engines, including 40HP (1984–1994), 50HP (1984–1987), Pro Series 50HP (1987–1990), and P50 models (1995–1996). It provides the necessary components to overhaul your engine's cooling system for reliable performance.

This kit serves as a direct replacement for Yamaha part numbers 6H4-W0078-A0-00, 6H4-W0078-00-00, and 6H4-W0078-01-00. It is also an aftermarket equivalent to Sierra 18-3429. For a kit that includes the housing, reference Sierra part 18-3408.

  • Installation Method: Installs as a direct OEM-style replacement.
  • Engine Compatibility: Designed for marine 2-stroke outboard cooling systems.
  • Complete Kit: Includes a new impeller, gaskets, wear plate, insert cup, water seal, and other hardware required for a standard rebuild.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Brand Part Number Notes
Yamaha 6H4-W0078-A0-00
Yamaha 6H4-W0078-00-00
Yamaha 6H4-W0078-01-00
Sierra 18-3429 Base kit without housing.
Sierra 18-3408 Kit with housing included.

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.

Brand Model Rated HP Stroke Years OEM Part No.
Yamaha Outboard 40 2-Stroke 1984-1994 6H4-W0078-00-00, 6H4-W0078-01-00, 6H4-W0078-A0-00
Yamaha Outboard 50 2-Stroke 1984-1987 6H4-W0078-00-00, 6H4-W0078-01-00, 6H4-W0078-A0-00
Yamaha Outboard Pro Series 50 50 2-Stroke 1987-1990 6H4-W0078-00-00, 6H4-W0078-01-00, 6H4-W0078-A0-00
Yamaha Outboard P50 50 2-Stroke 1995-1996 6H4-W0078-00-00, 6H4-W0078-01-00, 6H4-W0078-A0-00

Technical Specifications

Specification Value
Product Type Water Pump Repair Kit
Installation Direct OEM replacement
Housing Material Not included in base kit (housing sold separately)
Other Technical Attributes Compatible with marine 2-stroke outboard cooling systems

Package Contents

  • 1 x Water Pump Impeller (6H4-44352-00)
  • 1 x Woodruff Key (90280-03M03-00)
  • 1 x Cartridge Outer Plate (663-44323-00)
  • 1 x Insert Cup (663-44322-00)
  • 1 x Gasket (663-44315-A0)
  • 1 x Gasket (663-44316-A0)
  • 1 x Gasket (663-44324-A0)
  • 1 x Water Seal (93101-23070-00)
  • 2 x Bolt (97095-08045-00)
  • 2 x Bolt (97095-08045-00)

Installation Guide

  1. Safety First: Disconnect the battery and ensure the engine is in a secure, stable position.
  2. Drain Gear Lube: Place a drain pan under the lower unit and remove the upper and lower gear lube drain screws to drain the oil.
  3. Remove Lower Unit: Remove the mounting bolts securing the lower unit (gearcase) to the midsection. Carefully lower it to access the water pump.
  4. Disassemble Pump: Unscrew the bolts on the water pump housing and lift it off. You may need to gently pry it.
  5. Remove Old Components: Take out the old impeller, wear plate, gaskets, and seals. Note their orientation for correct reassembly.
  6. Clean Surfaces: Thoroughly clean all mating surfaces, removing any old gasket material or corrosion.
  7. Install New Parts: Place the new gasket and outer plate on the gearcase. Install the new insert cup into the housing.
  8. Install Impeller: Slide the new Woodruff key onto the driveshaft and install the new impeller, turning the driveshaft clockwise to bend the vanes correctly.
  9. Reassemble Pump: Apply a light coat of marine grease to the inside of the insert cup. Slide the housing down over the impeller and secure it with the new bolts and gaskets.
  10. Reattach Lower Unit: Guide the lower unit back into place, ensuring the driveshaft, shift shaft, and water tube align correctly. Fasten the mounting bolts.
  11. Refill Gear Lube: Fill the lower unit with fresh gear lube from the bottom drain hole until it seeps out of the top hole, then reinstall both screws.
  12. Test Operation: Securely attach a water source ("ear muffs") and run the engine to check for proper water flow and no leaks.

Troubleshooting & FAQ

How do I confirm this kit fits my engine?
First, check the "Compatible Engine Models" table on this page. Your engine's model, horsepower, and year range should be listed. Second, compare the part numbers in the "Part Number Cross-Reference" table to your existing part or service manual. Finally, visually compare our product photos with your old parts before ordering.

What are the signs that my water pump needs to be replaced?
Common signs of a failing water pump include the engine overheating, a weak or inconsistent stream of water from the "telltale" outlet, and visible cracking or deterioration of the impeller vanes upon inspection.

How often should I replace my water pump impeller?
For preventative maintenance, it is recommended to replace your impeller every 1-2 years or every 100-200 hours of operation, depending on usage conditions (e.g., saltwater vs. freshwater). Always consult your engine's service manual for specific intervals.

Does this kit include the water pump housing?
No, this is a basic repair kit that does not include the metal water pump housing. This kit matches Sierra 18-3429. If your housing is scored, warped, or cracked, you should purchase and install a new one separately. The kit that includes a housing is typically equivalent to Sierra 18-3408.

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.
Shipping Notes
  • Free Standard Shipping on $100+ Orders to the USA.
  • Except Preorder products are shipped in 48 hours.
  • Delivery to the USA:
  1. Standard Shipping : 3-10 business days
  • If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
  • We offer a 30-day return/exchange service after receiving.
  • Final sale items are not eligible for returns or exchanges.
  • To process your return/exchange, please contact us at [email protected]
  • Please click here for more details>>> Return & Exchange Policy
SKU: 91825021372

Discover Niche Categories That Outsell

Top-Converting Item to Boost Your Average Order

4.9 ★★★★★
Based on 12 reviews
Sort
Highest Rating
Newest First
Oldest First
Product Reviews
R
Verified Purchase
Robert&Robbie
Waukegan, US
★★★★★ 4
Great for indoor use.
Size: 10-11, Color: Cable Knit Navy
I bought a pair of these for myself about a year ago and there are plusses and minuses to them. They are comfortable and warm, without getting my feet sweaty or whatever. That's exactly what I wanted. On the minus side, mine ran far too small. I am a 10.5-11 shoe size and the 10-11 is about a half inch too short... my heels are sliding off the back. I am reordering a size 12-13 to try that one. In the take note column, the soles are NOT rubberized in any way. In fact they are like foam, and will absorb water! Also they do not provide cushioning against any kind of rough surface. I think they are perfect for strictly inside the apartment use, but they are not like moccasins or something that allow outdoor use. And I am ordering a 2nd pair after a year so I do like them.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on November 24, 2025
J
Verified Purchase
Jeffery Mercer
Belleville, US
★★★★★ 5
They are of great quality!
Size: 12-13, Color: Cable Knit Coffee
Love em! After a year and there still Great and warm and Cozy too!
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 26, 2026
C
Verified Purchase
Cecil W
Grantham, US
★★★★★ 5
Wonderful sock slippers
Size: 12-13, Color: Cable Knit Navy
These are wonderful sock slippers, They are very warm and well made. After reading reviews, I decided to order one size larger (10 to 11) and they are really comfortable big. However, I'm glad I did because they a lot easier to put on and take off. Highly recommended.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on April 20, 2026
J
Verified Purchase
Jimal
New York, US
★★★★★ 3
You get what you pay for
Size: 10-11, Color: Cable Knit Black
Comfy but cheaply made. I bought these for the price and expected them to be not the best quality but they are even less than I expected. Please also note that they run small. I got a 10-11 since I wear 11 shoe and Amazon recommended this size. I think a size larger would have been better. Not worth returning though. I’ll just wear them this winter if they last that long and get a better brand next time.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on December 25, 2025
L
Verified Purchase
L R
Draper, US
★★★★★ 5
I will buy these again.
Size: 12-13, Color: Cable Knit Brown
These are great. They’re warm and comfortable.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 5, 2026

recommand products