In the heat exchanger cooling system, the coolant is drawn by the engine water pump from the heat exchanger and is forced through the engine oil cooler, cylinder block, cylinder heads and exhaust manifolds to the thermostat housings. A bypass from the thermostat housings to the inlet side of the water pump permits circulation of coolant through the engine when the thermostats are closed. See Figure 35404 and see Figure 35405 .
When the thermostats are open, the coolant flows through the heat exchanger where it is cooled.
An engine driven raw water pump circulates raw water (sea water) through the heat exchanger to lower the temperature of the engine coolant.
Schematic of the Heat Exchanger-Cooled Pleasure Craft Marine Engine
Raw Water Flow on Heat Exhanger-Cooled Marine Engine