ok so we have a cruiser with a 7.4 454 mercruiser (1999). we let a friend borrow it to go fishing. The next time we went to use it, it was hard for the starter to turn it over, checked the oil... no signs of water in the oil. I've flooded many engines to know it was hydo locked. so i opened the throttle wide open and after a few spins it started up and i thought we were in the clear. oil pressure looked good so let it idol a few minutes and noticed the temp was getting higher than usual and a warning alarm went off near 200 deg so I shut it off and let it cool a bit. It would fire right back up and run smooth I then noticed that it had lost all oil pressure. so i killed the engine and checked oil again. this time found milky oil. So i figure it is a blown head gasket due to an overheat because I think the impeller went bad. Ive worked on many head gaskets but Ive never had a head gasket problem where i have lost ALL oil pressure. So is it possible that all my loss of oil pressure is due to major head gasket leaks or do I have a bigger problem such as bad bearings??? Thanks for any advice.
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