That scenario reminds me of the 12V-71TI's in the ferries that I used to run. Apparently, after an oil change, the filter housing did not properly seat and the engine promptly disposed of its 12 gallons or so into the bilge. Now, since we are talking about an engine that cost, at that time, over $35,000., there is an alarm in the pilot house that warns, audibly, of low oil pressure. The problem with the alarms is that the captains turn them off below 700 rpm because they go off due to low pressure at idle. So, the alarm is off and the captain makes it out of the marina, hooks up, and goes about four minutes and the engine just shuts itself down. Naturally, he never put the alarm on and never knew it was out of oil.

It actually started when it was returned back to the base. I was there for that event. Had a very rough and lumpy idle. The mechanic knew it was toast. Pistons, rings, liners. The crank, however, was OK. 40 hours of labor for two men which could have been avoided for want of a simple alarm that does what it should, without the need to turn it on and off.

So, if the 12V71 is any indication, the most likely culprit is going to be the pistons, rings and cylinders. Don't have the luxury of liners there so the engine probably has to come back out.