Can't have started in a boiler room - she was diesel.
There was a series of fires, mostly minor, onboard in 1971, which turned out to be the work of an arsonist, a young seaman. Started with silly little fires in gash bins, then the notice board, then got more seriious when he set fire to the tiller flat, and worst, the jungle mess, during the night after a good run ashore, when we were all sleeping very heavily. Mess filled very quickly with thick black smoke from uniforms and plastic suit bags - lucky no-one was badly hurt. But I don't remember it putting us out of action for any length of time.