Sierra 118-36140 Thermostat for Mercury 175-300HP Outboard Engines

The Sierra 118-36140 is a replacement thermostat designed for Mercury outboard engines in the 175–300 HP range. Sierra thermostats are engineered to meet or exceed OEM specifications, ensuring reliable coolant temperature regulation and optimal engine performance on the water.

Proper thermostat function is critical in marine outboard engines — it helps the engine reach operating temperature quickly, maintains consistent thermal efficiency, and protects internal components from overheating or running too cool. This direct-fit replacement simplifies installation and restores factory-level cooling system performance.

Key Features:

• Direct OEM replacement for Mercury outboard thermostats
• Designed for Mercury 175–300 HP outboard engines
• Meets or exceeds original equipment specifications
• Helps maintain proper engine operating temperature
• Manufactured by Sierra, a trusted name in marine replacement parts
• Cross-references OEM part number 18-36140

Sierra (part of Pleasurecraft Marine Engine Group / CDI Electronics) is a leading supplier of marine aftermarket parts, widely used by marine technicians and boat owners worldwide. The 118-36140 is a reliable, cost-effective solution for maintaining the cooling system on compatible Mercury outboard motors.