could survive that, but I would worry about the valve train a bit. You may end up pulling the head
and having it redone. Salt water
on the valve shafts and seats could be pretty bad.
You need to find out where the water gets in, we need to know more.
But it can siphon in from the exhaust. One lapping wave at a time.
Is there a riser?
is there a muffler
what is the exhaust layout?
was your engine
seacock closed while you were gone?
Is your stern open to wind
Can you bypass the oil cooler? Just do that. That will tell you something. Many engines dont have one anyway.
Get the old oil out of there and run that engine good and hot. You might remove the injectors and squirt some light oil in the cylinders and let it sit a couple days first.
Rechange the oil after running hot. Find that water ingress.