V8 overheating problem ( 5.7 mercruiser)

[76GMC1500]

With the 350 Chevy, head gasket problems are rare. *The motor is very good at holding on to head gaskets. *Even if the motor is fresh water cooled, a bad raw water pump will still cause overheating. *The raw water pump on a fresh water cooled engine is like the cooling fan in your car. *If that goes, you have no cooling water through the heat exchanger and your engine overheats. *The heat exchanger itself may also be plugged. *These are usually easily serviced. *After leaving the heat exchanger, the raw water is dumped overboard through the exhaust manifolds. *If these are plugged, there will be no water flow and the engine will overheat. Circulating pump problems are also very rare. *There just isn't much to go wrong inside of that pump. *