Sorry to hear this happened, When I lived up North, when they were done winterizing, they hung a tag(like the ones you see hanging from fire extinguishers) on the drive that said "Winterized", not sure if the marinas in your area do that, but If I didnt see one, I would have made damn sure it was done.

Main Mech and insurance Adjuster were out here today. They want the mech to take it and diagnose it further. They are hoping it is just the oil cooler. My concern is that they overlook something. Should I take the engine to someone else. Who I usually have do work on the engine is certified in merc up to 1000 HP. Or should I just let him take the boat and deal with it. he said if it was a blown engine, then he would not want to touch it. He said it is just a good engine with good internal parts, etc.

Engine is a crate 502 HO with upgraded parts, etc. Gill dry offshore exhaust, etc.

Someone certified is the way to go.