If you tried to start it but it would only turn a partial revolution, id say it has water in the cylinders which can cause damage such as broken rings, bent Con rods etc.
for starters you need to pull the injectors out and get the water out of the cylinders ASAP. Flush with crc, wd40 or similar. Next figure out how the water got there and solve that problem.
After you've sorted the water getting in and providing the motor turns over ok do a compression test to determine whether or not rings are broken etc.
If it checks out ok you should be able to change the oil, start it, run for a while, change the oil, repeat till you are happy all the moisture is out of it.
If compression is down, it will need pistons out for checking.

Schoonerriffic said..

If your boat is raw water cooled and you had the seacock opened whilst a lot of cranking, there is a high chance it back flowed water back into the engine...

Hope you don't mind if I try to understand the details of how this happens.
.
I assume the water comes from the filled up lift muffler, and gets into the cylinders via the exhaust manifold.
.
If that is the case, then why could the same thing not happen for a heat-exchanger cooled engine (i.e. not raw water cooled)?

Karsten said..

Schoonerriffic said..

If your boat is raw water cooled and you had the seacock opened whilst a lot of cranking, there is a high chance it back flowed water back into the engine...

Hope you don't mind if I try to understand the details of how this happens.
.
I assume the water comes from the filled up lift muffler, and gets into the cylinders via the exhaust manifold.
.
If that is the case, then why could the same thing not happen for a heat-exchanger cooled engine (i.e. not raw water cooled)?

As Unclebob said, it still can. A marine diesel "heat exchanger" is made for raw water systems even if it has a closed circuit using fresh water. There will always be a point where the exhaust gases mixes with the raw water upon exit. Where the gases meet with the raw water is where back flow happens if no back pressure.
The only time a marine engine runs complete fresh water is when it has a dry exhaust. Usually running along a keel or the underside of a hull, there is a long pipe with a series of bends that the fresh water flows through and is cooled by the surrounding sea water..

Schoonerriffic said..

Karsten said..

Schoonerriffic said..

If your boat is raw water cooled and you had the seacock opened whilst a lot of cranking, there is a high chance it back flowed water back into the engine...

Hope you don't mind if I try to understand the details of how this happens.
.
I assume the water comes from the filled up lift muffler, and gets into the cylinders via the exhaust manifold.
.
If that is the case, then why could the same thing not happen for a heat-exchanger cooled engine (i.e. not raw water cooled)?

As Unclebob said, it still can. A marine diesel "heat exchanger" is made for raw water systems even if it has a closed circuit using fresh water. There will always be a point where the exhaust gases mixes with the raw water upon exit. Where the gases meet with the raw water is where back flow happens if no back pressure.
The only time a marine engine runs complete fresh water is when it has a dry exhaust. Usually running along a keel or the underside of a hull, there is a long pipe with a series of bends that the fresh water flows through and is cooled by the surrounding sea water..

You need to change a head gasket and refresh the head. Check the piston.