Seawater getting into oil on Yanmar 1gm10

[snoozydude]

Howdy
I noticed my my dipstick was registering that the oil was far over full and when I started the engine the oil had turned a pale grey. Obviously it looks like seawater was getting in.
It has been tempremental of late stalling when put in forward until it has been running for a good few minutes. Ran fine in reverse then when put in forward it would stall.
I checked the net and have pulled off the exhaust elbow and it looks fine (thoug I do not know what a good one should look like) the exhaust elbow and head did not look blocked.

This incident happened the morning after I had gone for a 1 hour motor and slept overnight. I did leave the engine intake open overnight. I have seen some posts that suggest that you should start the engine with the seacock off then open it once the engine starts.

Would leaving the seacock open overnight have caused this?

What should I do other than drain and flush out the old oil and change the oil filter.

Thanks in advance.

 

[Tranona]

Could be a number of things. The exhaust tends to corrode in the inner tube - not always easy to spot from visual inspection. Take it off again, turn it upside down, block off the water injection pipe and fill the gap between the two tubes with water. There should be no leakage.

Do you have an anti syphon valve in the run from the outlet on the head to the injection point? This stops water getting back when you switch off. Leaving the seacock open on its own will not cause water to get into the engine.

Next thing to look at is the waterpump which has two seals, the inner one stops water from getting into the oil. The seals and shaft may need replacing.

More fundamental, if you have been sucking water and steam back into the engine it corrodes the exhaust valve and can corrode the head casting to the point that the water jacket perforates, letting more water in. Corroded valves can lead to poor starting and stalling at low speeds. It is a cylinder head off job to check valves.