Description

The Mercury / Quicksilver 8M0162139 Thermostat is a genuine OEM 140°F (60°C) thermostat designed for modern Mercury outboard engines.

This thermostat controls coolant flow through the engine, allowing it to warm up quickly and maintain a stable operating temperature under load. The 140°F calibration is specifically engineered for high-output outboard applications where lower operating temperatures are required for durability and performance.

It features a self-cleaning valve design, allowing debris and contaminants in the cooling system to pass through without sticking the thermostat closed. Combined with corrosion-resistant materials, this ensures long service life in saltwater environments.

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Key Features

• Genuine Mercury / Quicksilver OEM part
• 140°F (60°C) temperature rating
• Designed for modern 4-stroke outboards
• Self-cleaning valve reduces sticking/failure
• Corrosion-resistant construction for saltwater use
• Maintains proper engine temperature and efficiency
• Direct OEM replacement

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Engine Compatibility

Mercury 4-Stroke Outboards (Serial-Specific)

Fits engines including:

• 175 HP V6 (3.4L)
• 200 HP V6 (3.4L)
• 225 HP V6 (3.4L)
• 250 HP V8 (4.6L)
• 300 HP V8 (4.6L)
• 300R / 450R Racing models

Applies to engines with serial numbers:

• 2B529482 and newer

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Important Fitment Notes

• Designed for modern Mercury 4-stroke outboards only
• Used in raw water cooling systems
• Not compatible with older carbureted or 2-stroke engines
• Not interchangeable with 160°F or 170°F thermostats

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Specifications

• Part Number: 8M0162139
• Temperature Rating: 140°F (60°C)
• Type: Engine thermostat
• Operation: Wax-element valve
• Cooling System: Raw water cooled outboards
• Construction: Corrosion-resistant metal

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What’s Included

• Thermostat only
  (Seals/O-rings sold separately unless specified)

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When This Part Needs Replacement

• Engine overheating
• Engine running too cold (thermostat stuck open)
• Temperature fluctuations
• Debris-related sticking or corrosion
• Routine service on high-hour outboards

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Installation Notes

• Replace seals/O-rings at the same time
• Install with correct orientation
• Inspect cooling passages for debris
• Verify proper temp after install

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Alternate / Superseded Part Numbers

OEM Cross References

• Mercury / Quicksilver: 8M0162139
• Replaces: 8M0137816

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Shipping

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

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Parts Desk Insight

These newer Mercury thermostats rarely fail closed—most failures are debris-related sticking, so if you’re replacing one, it’s worth checking the whole cooling system