We have a friend who was well into a voyage across the Atlantic when the oil pressure alarm went off on her engine.
She and her crew made all the usual checks but to no avail.
When they finally got to the Azores under sail and with no engine for charging, the mechanic found parts of the seal from a bottle of oil blocking the lube oil pump pickup tube.
My guess is that someone had let these fragments drop into the container of oil, or maybe a whole seal, a surprisingly easy thing to do, and then dumped the oil into the engine.
It truly is the little things that can get you. And when they do on a voyage it sucks ten times more.
This kind of thing is one of the many reasons I have always done all the routine maintenance on critical systems like the engine myself, and would have done so even if we could have afforded to pay someone else.
Sure we all hope that the guy in the boatyard tasked with doing oil changes would be careful not to let this happen, and strain the oil if it did…