Part Number: 47-3667
Sierra 18-3667 Marine Thermostat
Maintain proper engine temperature and dependable cooling system performance with the Sierra 18-3667 Thermostat. Designed as a high-quality replacement for select marine engines, this thermostat regulates coolant flow to help your engine reach and maintain optimal operating temperature under varying conditions on the water.
The thermostat is a critical component in any marine cooling system. It controls when coolant circulates through the engine, helping improve engine efficiency while preventing overheating during extended operation. A worn or sticking thermostat can cause inconsistent temperature readings, poor fuel economy, hard starting, or overheating issues that may lead to expensive repairs.
Built using durable marine-grade materials, the Sierra 18-3667 is engineered to meet or exceed OEM specifications for reliable performance and long service life in harsh marine environments. Designed as a direct replacement, it provides dependable fitment and straightforward installation for routine cooling system maintenance.
Common Engine Fitments
The Sierra 18-3667 thermostat is commonly used on a variety of marine engine applications, including:
- MerCruiser 4.3L V6
- MerCruiser 5.0L V8
- MerCruiser 5.7L V8
- PCM Excalibur 5.7L
- PCM GT40 Ford 351
- Volvo Penta 5.0Gi and 5.7Gi engines
- OMC Cobra 5.0L and 5.7L applications
These engines are frequently found in:
- Sea Ray sport boats and cruisers
- Chaparral SSi models
- Four Winns Horizon series
- Malibu Wakesetter and Response boats
- Correct Craft Ski Nautique and Super Air Nautique
- Supra Launch and Sunsport models
Fitment can vary depending on cooling system design and engine serial number, so confirming compatibility with part number 18-3667 before ordering is recommended.
Key Features
- High-quality marine engine thermostat
- Helps maintain proper engine operating temperature
- Restores dependable coolant circulation and cooling efficiency
- Compatible with MerCruiser, PCM, Volvo Penta, and OMC applications
- Marine-grade construction for durability and reliability
- Direct replacement for straightforward installation
Why Replace a Marine Thermostat?
Over time, thermostats can stick open or closed from repeated heat cycles and corrosion exposure. Replacing a failing thermostat helps maintain stable engine temperatures, improve cooling system performance, and reduce the risk of overheating-related engine damage.
If you’re servicing a compatible inboard or sterndrive marine engine, the Sierra 18-3667 thermostat delivers dependable cooling performance and OEM-style reliability you can trust.