Sierra 18-3434 Water Pump Kit for Yamaha Outboard, Replaces 63D-W0078-01-00, Without Housing

The Sierra 18-3434 is a water pump repair kit built for Yamaha outboard motors, supplying the core wear components needed to restore cooling system pressure and flow without replacing the entire pump housing. This kit is sold without the housing itself, so it is intended for rebuilding an existing pump body rather than a full pump replacement -- Sierra offers the same kit with the housing included under part number 18-3145 for buyers who need that additional piece.

Inside the kit you get the impeller, the pump case gasket, and the wear plate, the three parts that wear out fastest in a water pump and are the most common cause of overheating or reduced water flow. The impeller is the flexible-vane component that actually pumps raw water through the cooling passages, the wear plate provides a smooth, flat surface for the impeller vanes to seal against, and the gasket seals the pump case to prevent leaks and pressure loss. Replacing all three together, rather than piecemeal, is the standard approach for a proper pump rebuild since they wear as a set.

The 18-3434 is designed as a direct equivalent to Yamaha OEM part 63D-W0078-01-00 and is cross-referenced to 63D-44311-00-00 as well, so it drops into applications calling for either Yamaha number. It fits a range of Yamaha outboard models as detailed below.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3434
• Product Type: Water Pump Repair Kit (Without Housing)
• Weight: 0.35 pounds
• Kit Includes: Impeller, Pump Case Gasket, Wear Plate
• Impeller OEM Number: 697-44352-00-00
• Pump Case Gasket OEM Number: 63D-44316-00-00
• Wear Plate OEM Number: 63D-44323-00-00
• OEM Cross Reference: 63D-W0078-01-00, 63D-44311-00-00
• Compatible Engine Brand: Yamaha Outboard
• Companion Kit (With Housing): Sierra 18-3145

Fitment

• Yamaha 40/50 hp (1995-03)
• Yamaha P40 (1998)
• Yamaha C40 3 cyl (1997-02)
• Yamaha C50 (1999-01)
• Yamaha F40 2.6L (1999)
• Yamaha F50 (1995-03)
• Yamaha P50 (1995-96)
• Yamaha F60 (2002-03)

Replaces (OEM)

• 63D-W0078-01-00
• 63D-44311-00-00

Frequently Asked Questions

What does the Sierra 18-3434 water pump kit include? The kit includes an impeller, a pump case gasket, and a wear plate, the three components most commonly replaced during a Yamaha outboard water pump rebuild. It does not include the pump housing.

Does the 18-3434 come with the pump housing? No, this kit is sold without the housing. Sierra part number 18-3145 is the same kit but with the housing included, for buyers who need to replace that part as well.

Which Yamaha outboards does the Sierra 18-3434 fit? It fits Yamaha 40/50 hp (1995-03), P40 (1998), C40 3 cyl (1997-02), C50 (1999-01), F40 2.6L (1999), F50 (1995-03), P50 (1995-96), and F60 (2002-03).

What OEM Yamaha part numbers does 18-3434 replace? It replaces Yamaha OEM numbers 63D-W0078-01-00 and 63D-44311-00-00, so it is a direct fit anywhere either of those numbers is called for.

Is the impeller in this kit a separate part number? Yes, the impeller included in the 18-3434 kit corresponds to Yamaha OEM number 697-44352-00-00 and is supplied as part of the full kit rather than sold separately in this listing.

How much does the Sierra 18-3434 water pump kit weigh? It weighs 0.35 pounds.

Is the wear plate included, and what OEM number does it match? Yes, a wear plate is included in the 18-3434 kit and matches Yamaha OEM number 63D-44323-00-00.

What is the gasket OEM number in this kit? The pump case gasket included with the Sierra 18-3434 matches Yamaha OEM number 63D-44316-00-00.

Is Sierra 18-3434 a genuine Yamaha part or aftermarket? The 18-3434 is a Sierra-manufactured kit designed as a direct equivalent to Yamaha OEM numbers 63D-W0078-01-00 and 63D-44311-00-00, not a genuine Yamaha-branded part.

When would I need 18-3145 instead of 18-3434? Choose 18-3145 if your pump housing itself is damaged and needs replacing; 18-3434 is the same rebuild kit but without the housing, for when the housing is still serviceable.

Does this kit fit both 2-stroke and 4-stroke Yamaha models? The 18-3434 fitment spans models like the 40/50 hp, C40, C50, P40, P50, F40 2.6L, and F60, covering the specific Yamaha model years listed rather than a single engine type.