Description

The Sierra 18-3056 Impeller (AP-1814) is a direct replacement raw water pump impeller designed for Mercury and Mariner outboards. This impeller is responsible for circulating cooling water through the engine, ensuring proper temperature control and preventing overheating.

Built to meet or exceed OEM specifications, this impeller features durable, flexible rubber vanes and a precision-fit hub for reliable performance in both freshwater and saltwater environments.

Routine replacement of the impeller is essential to maintain optimal cooling efficiency and protect your engine from heat-related damage.

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Key Features

• Direct replacement raw water pump impeller
• Flexible rubber vanes for efficient water flow
• Precision-fit hub for secure installation
• Maintains proper engine cooling performance
• Marine-grade construction for durability
• Sierra limited lifetime warranty

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Engine Compatibility

Mercury / Mariner Outboards

Commonly used on:

• 25 HP
• 30 HP
• 35 HP

Fits select Mercury/Mariner 2-stroke outboards using compatible water pump assemblies.

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Serial Number Fitment Notice

Fitment depends on:

• Engine model and year
• Water pump housing design
• Shaft configuration (keyed vs splined)

Always confirm using:

• Engine serial number
• OEM part number match (18-3056 / AP-1814)

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When This Part Needs Replacement

Replace the impeller if you notice:

• Weak or no telltale stream
• Engine overheating
• Reduced cooling performance
• Cracked, hardened, or missing vanes
• After seasonal storage

Recommended service interval: every 100 hours or annually

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Installation Notes

• Lubricate impeller before installation
• Install vanes in correct rotation direction
• Inspect housing and wear plate
• Ensure proper hub alignment (key or spline)
• Replace seals or gaskets if worn

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Alternate / Superseded Part Numbers

OEM Cross References

• Mercury: 47-89982, 89982T, 89982T1

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Aftermarket Cross References

• Sierra: 18-3056
• Mallory: 9-45604
• GLM: 12016

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Shipping

Shipping: Ships same or next day for fast Canada wide shipping.

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Parts Desk Insight

A worn impeller can still move water at idle but fail when you increase throttle. If your engine runs hotter at speed, this is often the cause.

Replacing it regularly is a simple way to keep your outboard running cool and avoid unexpected breakdowns