USCG Exam PracticeDiesel engine principles (motor propulsion)
In a marine diesel's indirect cooling system, what is the primary purpose of the thermostatic (temperature-regulating) valve?
- A. To regulate seawater flow through the sea suction strainer
- ✓ To bypass the jacket-water cooler until the engine reaches operating temperature, then admit jacket water to the coolerCorrect
- C. To control the flow of treated fresh water into the expansion tank
- D. To limit raw-water pump discharge pressure during high-load operation
Why B is correct
The thermostatic valve bypasses the cooler while the engine is cold, allowing it to warm up quickly, then progressively admits jacket water to the cooler as temperature rises, holding the outlet temperature in a narrow band regardless of load or sea temperature.
Cited:NAVEDTRA 14075 §3-5