The story goes like this....the mechanick that did the engine conected the belts wrong..from what i see...he used only one belt to drive the water pump..the seckond belt was going only from the crank to the impeler/fuel pump and back to crank(not on water pump).So when the belt that drives the water pump broke the engine did not shut down cousing it to owerheat..you see now why im learning things from you guys

Overheating does not happen instantly.
Your friend needs to learn to scan his gauges regularly or install some warning alarms (low oil pressure, high coolant temp).

Most twin engines boats have one engine with one v belt. Ie: the one without power steering pump.

Most serpentine belted engines have one belt.

Like said just above, gauges are meant to be looked at.