Part Number: 985009
Indmar 985009 Thermostat
Maintain proper engine temperature and reliable cooling system performance with the Indmar 985009 Thermostat. Designed as a genuine OEM replacement, this thermostat regulates coolant flow through the engine to help ensure consistent operating temperatures in demanding marine conditions.
A properly functioning thermostat is critical for engine efficiency and long-term reliability. When a thermostat begins to fail, it can cause overheating, inconsistent temperature readings, poor fuel economy, or slow engine warm-up. Replacing a worn thermostat helps restore proper coolant circulation and protects internal engine components from unnecessary heat and stress.
Manufactured to Indmar factory specifications, the 985009 thermostat is engineered for dependable operation in high-load marine environments. Designed as a direct-fit replacement, it installs easily and delivers the cooling performance your engine was designed to maintain.
Common Engine Fitments
The Indmar 985009 thermostat is commonly used on a variety of GM-based Indmar marine engines, including:
- Indmar Assault 5.7L
- Indmar Monsoon 325
- Indmar Monsoon 340
- Indmar Assault 325
- Indmar 5.0L MPI
- Indmar 5.7L MPI
- Select Indmar 6.0L engine applications
These engines are frequently found in popular towboats and wake boats, including:
- Supra Launch series
- Supra Sunsport and 21V models
- Moomba Mobius LSV
- Moomba Outback and Mojo
- Malibu Wakesetter models with Indmar power
- MasterCraft boats equipped with Indmar engines
The 985009 thermostat is commonly used in freshwater and closed-cooling system configurations where maintaining stable engine temperatures is essential for performance and reliability.
Fitment can vary depending on engine serial number and cooling system setup, so confirming compatibility with part number 985009 before ordering is recommended.
Key Features
- Genuine Indmar OEM thermostat
- Maintains proper engine operating temperature
- Helps improve cooling system efficiency and reliability
- Designed for GM-based Indmar marine engines
- Marine-grade construction for long service life
- Direct-fit 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 proper coolant flow, stabilize engine temperatures, and reduce the risk of overheating-related engine damage.
If you’re servicing an Indmar-powered Supra, Moomba, Malibu, or MasterCraft, the 985009 thermostat delivers the OEM-quality fit and dependable cooling performance your engine depends on.