Overheating has got to be one of the most common ways a marine engine bites the dust. Lack of maintenance is probably the main culprit. Impellers, hoses, hose clamps, water pump
belts and circulating pumps
can all fail and it doesn't take very long to cause damage if at high rpm. Mostly a matter of maintenance to prevent failures and just using the good old eyeball on a regular basis to look things over. The alarms
that warn of a lack of raw water seem like a good idea, although I haven't installed one yet.