Hi,
"If memory serves, the two stroke cycle "Jimmy" (GMC) diesel, which has a blower for exhaust scavenging, also has oil pressure to the blower shaft bearings, and if an oil seal adjacent to one of those blower bearings goes out, the engine will run just fine on that lube oil, ever increasing in rpm (read run-away diesel) until the engine finally blows up. They say that this is an especially terrifying situation in the engine room in a ship. Only thing you could do is somehow, quickly and completely choke off the intake air to the run-away engine before it blows up.."
Retired second class marine engineer here..
Dunno from where that come but what I read above is a non-sens
Just check a drawing of a marine diesel engine turbo blower (Brown Boveri or Stal Laval EG) and you will understand.
About overspeed (or overload).. it's auto protections for set immediately the engine in slow down ( not stop!) acting on fuel pumps and inlet forced air and a auto change from heavy fuel to diesel oil .. when T° meet requirement (monitored by the Graviner)
In fact all this is monitored by computer.
The stop of the engine will be performed by a other monitoring if the slow dow process fail.
And finally it's a ultimate mechanical protection if all fail (based on centrifugal force) for stop the engine.
All this apply for main engine or the diesel generators.(expet the fuel change for the diesel generators)