Sierra 18-3074 Neoprene Impeller, 6-Fin, for Yamaha Outboard Motor, Replaces 47-84027M

The Sierra 18-3074 is a neoprene water pump impeller built for Yamaha outboard motors. As the impeller inside the water pump housing, it is the component responsible for pulling raw water through the lower unit and pushing it up to cool the powerhead; a worn, cracked, or missing fin on the impeller is one of the most common causes of overheating in an outboard. The Sierra 18-3074 features 6 fins molded in durable neoprene rubber, a material chosen for its flexibility and resistance to heat and wear as it spins against the pump housing wall. Sierra manufactures this impeller to meet or exceed the quality of the original equipment part it replaces, so it installs the same way and delivers the same water flow as the OEM component. This impeller is intended for use on Yamaha outboard motors and is also cross-referenced to equivalent parts from GLM, Mallory, and Mercury Marine, making it a straightforward replacement whether the original impeller was a Yamaha, Mercury, or other branded part. Because water pump impellers are fit-specific, buyers should confirm the existing part number on their pump before ordering to ensure proper fit. Routine impeller replacement, typically as part of scheduled water pump maintenance, helps prevent overheating damage and keeps the cooling system operating as designed.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3074
• Product Type: Water Pump Impeller
• Material: Neoprene
• Number of Fins: 6
• Color: White
• Quantity: 1 impeller per package
• Weight: 0.01 pounds
• UPC: 030999315267
• OEM Cross Reference: 47-84027M
• Fitment: Yamaha outboard motor

Fitment

Designed for Yamaha outboard motors. Confirm the existing impeller part number on your water pump before ordering to ensure proper fit.

Replaces (OEM)

47-84027M

Frequently Asked Questions

What does the Sierra 18-3074 impeller fit? The Sierra 18-3074 is designed for Yamaha outboard motors. Since water pump impellers are fit-specific, confirm the part number on your current impeller before ordering to make sure the 18-3074 matches your pump.

What OEM part number does the Sierra 18-3074 replace? It replaces OEM part number 47-84027M. Buyers can order the Sierra 18-3074 as a direct equivalent to that original Mercury Marine part number.

How many fins does this impeller have? 6 fins, molded in neoprene rubber. The fin count and material match the design of the original equipment impeller it replaces.

What material is the Sierra 18-3074 impeller made from? Neoprene rubber. This material is used because it flexes without cracking under the friction and heat generated inside a running water pump housing.

How much does the Sierra 18-3074 weigh? The impeller weighs 0.01 pounds, consistent with a small single-component water pump part.

Is the Sierra 18-3074 a genuine Yamaha part or an aftermarket part? The 18-3074 is a Sierra-manufactured impeller, not a Yamaha-branded part. Sierra builds it to meet or exceed the quality of the original equipment impeller it replaces.

How many impellers come in one Sierra 18-3074 package? One impeller ships per package under part number 18-3074, ready to install as a direct replacement.

What color is the Sierra 18-3074 impeller? It is white, which is the standard color Sierra uses for the neoprene compound in this impeller.

When should I replace the impeller on my Yamaha outboard? An impeller like the Sierra 18-3074 should be replaced any time it shows cracked, torn, or missing fins, or as part of routine water pump service, since worn fins reduce raw water flow and can lead to overheating.

What is included when I order the Sierra 18-3074? The order includes one Sierra 18-3074 neoprene impeller. It does not include the wear plate gasket or woodruff key, which are separate parts in the water pump kit.

Will the Sierra 18-3074 fit a Mercury outboard as well? The Sierra 18-3074 is built for Yamaha outboard motors, but it is manufactured as an equivalent to OEM part 47-84027M, so it is compatible with equipment that originally used that part number. Always verify against your existing part number before ordering.