USCG Exam PracticeDiesel engine principles (motor propulsion)
In a marine diesel indirect cooling system, the thermostatic (temperature-regulating) valve serves what primary function?
- A. It regulates seawater flow through the sea suction strainer to prevent overheating
- ✓ It bypasses the jacket-water cooler until the engine reaches operating temperature, then admits jacket water to the cooler to hold outlet temperature in a narrow bandCorrect
- C. It controls the flow of treated fresh water into the expansion tank to maintain correct system pressure
- D. It diverts jacket water away from the lube-oil cooler when lube-oil temperature falls below the minimum operating limit
Why B is correct
NAVEDTRA 14075 §3-5 describes the thermostatic valve as bypassing the cooler while the jacket water is cold and then admitting it to the cooler as the engine heats up, holding outlet temperature steady regardless of load or sea temperature. This prevents both overcooling and overheating.
Cited:NAVEDTRA 14075 §3-5