Had only a couple of freezes, noting too hard. Went to winterize. Pulled the drain plug from the block and the one from the manafold. Filled with antifreeze. Pulled the back plug to fog the cylinder and antifreeze rdrained out of the spark plug hole. The engine ran good the last time we used the boat a couple of months ago. Well I am thinking it might be one of the following: cracked head, blown head gasket, or the block. What do you folks think? Any input would be helpful before I go to pull the head off. Thank you, 