Description

The Sierra 18-3065 Impeller (AP-2174) is a high-quality raw water pump impeller designed for Mercury and Mariner outboards. This impeller is responsible for circulating cooling water through the engine, helping maintain proper operating temperature and preventing overheating.

Constructed from durable, flexible rubber and engineered to meet or exceed OEM specifications, this impeller ensures consistent water flow and long service life in both freshwater and saltwater environments.

Ideal for routine maintenance, replacing your impeller helps restore full cooling system efficiency and protects 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:

• 20 HP
• 25 HP
• 30 HP

Fits select 2-stroke and early 4-stroke Mercury/Mariner outboards using compatible pump housings.

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Serial Number Fitment Notice

Fitment depends on:

• Engine model and year
• Water pump housing type
• Shaft spline/key configuration

Always confirm using:

• Engine serial number
• OEM part number match (18-3065 / AP-2174)

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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 with correct vane rotation
• Inspect pump housing and wear plate
• Ensure proper key or spline alignment
• Replace seals/gaskets if worn

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Alternate / Superseded Part Numbers

OEM Cross References

• Mercury: 47-89984, 89984T, 89984T1

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Aftermarket Cross References

• Sierra: 18-3065
• Mallory: 9-45603
• GLM: 12019

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Shipping

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

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Parts Desk Insight

If your engine is running a little warmer than usual or the telltale stream looks weaker, the impeller is often the cause. They wear gradually and can fail under load before showing obvious signs.

Replacing it regularly is one of the simplest ways to keep your outboard reliable and ready to go