Water in cylinders - How?

[Another retired guy]

Buddy of mine at next dock along came in from a run on the lake at idle speed. Said the engine was overheating. He shut it down and came back a few hours later to find that now it wouldn't crank. After checking usual electrical connections he removed one plug and saw water in the cylinder. He removed the remaining plugs and cranked it - water came out of all cylinders!
Marina says problem most likely a failed water pump and water has entered cylinders via the exhaust valves.
I am puzzled How can an engine be idling fine at shut-down and then suck water into ALL cylinders when it's stopped?
Can someone please explain this?
Boat is an early 80's Sea Ray with ( I think ) a 4.3 Mercruiser.
Thanks.

 

[tpenfield]

Re: Water in cylinders - How?

My engine did that . . . now it is toast.

It could be reversion and/or it could be that when the hot air in the cylinders cooled and contracted, it pulled water up the exhaust into the manifolds.

I had it happen on one side, but your buddy have it happen on both sides of the engine?

 

[Don S]

Re: Water in cylinders - How?

Well, if it overheated and he shut it off hot and the idle rpm was too high, it probably dieseled and sucked water back in through the exhaust. Happens all the time.

 

[sharkin95]

Re: Water in cylinders - How?

rapid boat de-acceleration,engine run on,no water shutters in exhaust,does this boat have thru the hull exhaust? check the oil to see if water is in the oil pan.

 

[Another retired guy]

Re: Water in cylinders - How?

Ok Thanks. I'm starting to see how this can happen. I don't have all the details of his boat but he did say that the oil was fine - water only on top of pistons

 

[Don S]

Re: Water in cylinders - How?

Here is a Service bulletin from Mercruiser on water intrusion.

View attachment 01-13 Gas Engines and Water Intrusion.pdf

 

[Another retired guy]

Re: Water in cylinders - How?

Thanks for that service bulletin. I'm new to boating this year and have learned a LOT from these forums. Certainly learned some new things today!
Thanks all.

 

[Levinz11]

Re: Water in cylinders - How?

Here is a Service bulletin from Mercruiser on water intrusion.

View attachment 160925

Thats good to have.