Cummins 6.3 with water in engine oil

She could try, but her odds aren't good, especially with salt. The harm could be a cracked block and a replace instead of a rebuild.

Salt is worst obviously. Depends on how much there is and long it s been sitting. They need to replace the oil right away and crank it without starting to circulate the fresh oil

years ago, i got salt water inside my generator due to a poor installation (no vented loop). Water syphoned in, filled the muffler and backed up in the engine. I noticed right away and was able to immediately drain, filled with diesel, circulate, repeat a couple of times and then again a couple of time with oil. Saved the motor

in this case the question is to know if it’s coolant or salt. Coolant would be a head gasket or possibly a cracked head. Salt would be intercooler.

first thing after changing the oil would be to pull the intercooler and pressure test it. I would do that before pulling the head.

I don’t see how a cracked block would result in salt water in the oil. Coolant yes but not raw water.

After salt dries on the cylinder walls and pistons what happens next?

That s why flushing with diesel and oil has to be done right away. Usually within 24 hours before corrosion starts. Cranking without starting with diesel helps flush the salt. After 24 hours it’s too late

If you read the OP it's well past 24 hours already.

Still remember as a kid when a friend dumped his OB into the bay. Out of the water and into a barrel of oil immediately. No problem. Any time a motor ingests or is submerged in salt water pickling it in oil (or diesel) immediately is a must. Don't suppose that mechanic flooded the motor with oil did he? (would have been good)

Most likely a head gasket from the overheating.......did she say exactly how hot it got? You'd have to further diagnose it to see.....could pull the injectors and do a compression test.

This situation brings RER's post #13 from https://www.yachtforums.com/threads/leaking-shaft-seal.33223/#post-297314
to mind.
If the engine is running to flush, it sounds hopeful.

Yep, pull the injectors and dump marvelous into each cylinder.

If the raw water pump is gear driven, perhaps that's how the water got in there......if it ate the shaft bearings......she might get lucky.

Generally they should leak out the weep holes when they fail and not in the crankcase, but if it severely ate the bearings, it's possible it could fill the crankcase (in a 1 in a 1000 chance). How hot the motor got before shutting it down and the load it had at the time will be the deciding factor.