[toewsrus]

Sea Water in the engine. Water Lock, Liquid Lock, whatever you call it, it's not good and will ruin your engine. I have the 3GM30F as well. does yours have an F at the end of the model number, meaning it's freshwater (antifreeze) cooled, or is it strait seawater cooled and no F?

I went to a 3 day Yanmar course last week, I think it was one of the first things he told us: don't crank your engine longer than 20 seconds total (5 seconds now, 5 later, 5 later on and then 5 more) (or 20 seconds all at once). If you do, the muffler must be drained. The seawater will accumulate and not get pushed out by the cranking engine. It's a running engine's exhuast pressure that pushes the seawater overboard.

Liquid Lock will bend or break your connecting rods. I'm not sure of the extent of your damage. But if it's running, I would start with an oil change, then another, and probably a good once over by your mechanic.

If it's not a freshwater cooled (No F after the 3GM30) and the water is coming in by itself and not because of over cranking, I would suspect a blown gasket or crack in the head or block. Either way it involves major engine work.

Please let us know how it goes!