Description
SIERRA 120°F Mercury 40-60 HP Outboard Thermostat – 18-3640
The SIERRA 120°F Mercury 40-60 HP Outboard Thermostat – 18-3640 is a marine cooling-system replacement component designed for Mercury 40-60 HP outboards, serial 1C050252 and up. Its 120°F (49°C) operating rating helps the engine reach and maintain the intended cooling-system temperature. It is a fit-specific service part; confirm the engine model, serial range, cooling configuration, and OEM interchange before installation.
- Designed for Mercury 40-60 HP outboards, serial 1C050252 and up
- Thermostat temperature rating: 120°F (49°C)
- Helps regulate coolant flow as the engine reaches operating temperature
- Direct-fit replacement for the specified marine engine applications
- Suitable for preventive maintenance or replacement of a sticking/corroded thermostat
Specifications
- Manufacturer: Sierra
- Part Number: 18-3640
- Product Type: Thermostat
- Application: Mercury 40-60 HP outboards, serial 1C050252 and up
- Temperature Rating: 120°F (49°C)
- OEM / Aftermarket Interchange: Mercury Marine 8M0117413, 8M0168892
- UPC: 808282375454

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