My 40hp mariner started idling poorly recently. I pulled the spark plugs and found that there was a milky substance on plugs 3 & 4, and the same milky colored substance was running out of the exhaust relief ports. I thought that the exhaust cover gasket may have been bad and leaking water in through the exhaust ports in the cylinders, so I replaced the cover gaskets, as well as the water jacket gasket. This, however, did not help. I am at a loss here. If the powerhead mounting gasket were bad, could water somehow make it into the cylinders? I am fairly certain that the block is not cracked, as all 4 cylinders had 110lbs of compression, and the cylinders are not "full" of water. Any thoughts?
