In marine diesel engine installations, automatic temperature control by means of thermostatically operated bypass valves is more common than control by means of throttling valves in the seawater circuit. When used in the jacket-water system, these valves are located between the point where the jacket water leaves the engine block and the component that cools the water. The thermostatic valves used in the cooling systems of engines are of two types: the conventional type, which is also used in automotive engines (an example of this type is shown in fig. 7-16); and the three-way proportioning type (figs. 7-17 and 7-19). Valves of the latter type are commonly called automatic temperature regulators. Conventional thermostatic valves are generally used in small engines; the automatic temperature regulators are commonly used in medium and large engines.

Figure 7-17.-Automatic temperature regulator.