Depends. Cooling water is pumped up through the cooling system and then into the exhaust system. The small pump is not strong enough to pump water up and out the exhaust so it backs up and may reach the exhaust valves. As the engine turns the exhaust valves open and water pours in, eventually filling the cylinder. Water does not compress, so the engine stops turning. This is called hydro locking. It can be quite destructive to the engine if it locks up while turning. To empty the cylinders, the injector (or spark plug in gas engines) is removed and the engine turned over. The water will exit the injector holes. If you are lucky and there is no other damage you put everything back together and go sailing.The manual does speak to excessive attempts. What's excessive?
Check the water lift muffler, there maybe a drain plug on the bottom, open it and let the water drain out. That might be the easiest way. Or take remove the hose that goes in to the injection elbow. If that is full of water it may have backed up into the exhaust manifold. Try turning the flywheel. If it goes around twice it should be fine. Find the compression release and release the compression, that will make it easier to turn.I would like to ask what actually needs to be inspected for trapped water? Do not believe I made too many attempts but feel it's worth it to inspect.
Using that little priming pump lever? About 3 days
Does your Racor have the priming pump on it? That moves more fuel and will fill the filter body and move the fuel to the secondary filter bleeder. Once you have all fuel (no bubbles) there, you should be able to start it. If not you have to start loosening injector nuts. Generally the engine is self priming once you get all fuel to the engine filter.
You can also have someone do the starting part and you stay below with the bleed screw open with rags around it......One trick I found with my yanmar (3ym20)...
It was very hard to prime the system after changing filters... there was just too much air in the primary that the little yanmar lever on the injection pump couldn't suck out no matter how many full pumps I gave it. And there was no easy way to add fuel to the system directly into the racor filter housing itself.
However, I figured out that if I started the engine after the changing the filters, the engine would do the job of priming the racor. The engine would soon die as the air reached the injectors, but now, it could be fully primed and bled in just a few pumps of the finger lever. I've done four filter changes like this and it works every time like a charm.
I'm with the Yanmar tech. As I understand it the risk is that water will get into the cylinders and lock them. If the Pistons were able to make their full travel and combustion happened, I don't see how there could still be water there.The good news, the engine is running. The fuel solenoid was stuck so it was not air in the fuel injector as two mechanics suspected. Need your opinion though on the following....the Yanmar certified service tech said if there was water in the engine after some attempts to start it with the intake open, it would have flushed through while he ran the engine. Again, I'm not on board, but he said he ran it for quite a while and it would have stopped if there was an issue.
However, prior to leaving the matter in the hands of this Yanmar specialist to head home, a different mechanic said it would not push the water through. Thoughts?