Pull the hose off the oil cooler. I found back flushing won’t get everything out. The oil cooler has a honeycomb center and I had to dig the debris out. The oil cooler is what the out flow from the sea pump goes to first. The claims bolt is 10mm.

You should listen to this guy. I think he is right. I know that I just went through this today. On Friday I took a ride and at the end of the ride the port engine went to 200° and the red warning light lit up. Fortunately , it was right when we were in front of the dock. I quickly docked the boat and turned the engine off. Both water pressure gauges were at very strange readings too. I called the marina this morning and the came out immediately. The guys changed both impellers. We went for a test ride and nothing changed. One of the techs had just been through a similar issue with a formula. So, he checked the gaskets at the end of the heat exchangers. He showed me the gasket. It looked like a big glob of black glue and was starting to break up into pieces. They changed all four. My son and I just took a test ride. Both the water temp and the water pressure are back to normal. Simple fix and took about ten minutes for all four to be replaced.