The Raw Water Pump (rear half of 15/1) draws outside raw water from the sea cock and strainer and pushes it through a hose

(16/13), into the Heat Exchanger (16/1). As it passes through the Heat Exchanger it absorbs heat from the fresh water coolant. The raw water is then discharged into the Exhaust Elbow where it is sprayed on the hot exhaust gases to cool them. It then flows with the exhaust gas into the typical "wet marine" exhaust system.

CAUTION
Whenever the engine is cranked, the Raw Water Pump continues to pump water through the raw water system. With continued cranking, it is possible to fill the Exhaust Percolating Muffler, the Exhaust Hose, the Exhaust Elbow, and if the Exhaust Valve is open, the engine combustion chamber, with raw water. If the raw water is sea water, the damage to the engine can be severe. If this ever happens, corrective action must be taken at once. If the engine will not start within 7 to 10 seconds, stop cranking!