Description

The Mercury / Quicksilver 8M0117413 Thermostat is a genuine OEM 120°F (48.8°C) thermostat used on small-to-mid horsepower Mercury 4-stroke outboards.

This thermostat regulates engine temperature in raw water cooled systems, allowing the engine to warm up quickly while preventing overheating under load. The lower 120°F rating is specific to these engines and is required for proper fuel mapping, combustion efficiency, and corrosion control.

It uses a wax-element valve that opens progressively with temperature, ensuring stable cooling performance across idle and high RPM operation. Built to OEM standards, it provides reliable operation in both freshwater and saltwater environments.

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Key Features

• Genuine Mercury / Quicksilver OEM part
• 120°F (48.8°C) temperature rating
• Designed for raw water cooled outboards
• Maintains proper operating temperature
• Prevents overheating and cold-running issues
• Corrosion-resistant construction
• Direct OEM replacement

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Engine Compatibility

Mercury / Mariner 4-Stroke Outboards

Fits:

• 35 HP EFI (4-stroke)
• 40 HP EFI (4-stroke)
• 50 HP EFI (4-stroke)
• 60 HP EFI (4-stroke)

Typically applies to engines:

• Serial range: 1C453840 and newer

Common on:

• Mercury 4-cylinder EFI platforms
• SeaPro variants in same HP range

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Important Fitment Notes

• Raw water cooled systems only
• Must match OEM temp rating (120°F)
• Not interchangeable with 140° / 160° thermostats
• Superseded by 8M0168892 (updated design)

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Specifications

• Part Number: 8M0117413
• Superseded By: 8M0168892
• Temperature Rating: 120°F (48.8°C)
• Type: Engine thermostat
• Cooling System: Raw water cooled
• Operation: Wax-element valve

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What’s Included

• Thermostat (gasket/seal sold separately unless specified)

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When This Part Needs Replacement

• Engine overheating
• Engine running too cold
• Temperature fluctuation
• Debris or corrosion causing sticking
• Routine service interval

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Installation Notes

• Install with correct orientation (spring toward engine)
• Inspect and replace seals/gaskets
• Check cooling passages for debris
• Verify operating temperature after install

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Alternate / Superseded Part Numbers

OEM Cross References

• Mercury / Quicksilver: 8M0117413
• Supersedes to: 8M0168892
• Sierra: 18-3640

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Shipping

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

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Parts Desk Insight

These smaller EFI Mercs are very sensitive to thermostat temp—installing the wrong rating (like 140°) will throw off fuel mapping and cause poor performance