There are several types of overload to consider:
A. Catastrophic: something has gone very wrong. There may be a phase to phase short or two shorts to ground. This assumes you have an ungrounded system. With luck the main circuit breaker will open without destroying itself;
B. Steady state over current: The load on the generator is greater than the rating on the circuit breaker. Time to parallel in another generator
or shed load;
C. Transient over current: Suppose you were running two generators in parallel and one failed. The remaining machine may experience an over current condition that causes the breaker to trip. You can also have transient breaker trips upon activation of a large motor e.g., fire pump or bow thruster;
D.Thermal: There is a big difference in sea water temperature as you travel the world. It is possible to have an overload caused by the diesel engine's inability to shed heat in the tropics. Continued operation could damage the diesel engine. Again, parallel in another generator or shed load.