volvo penta 5.7 variable temp readings when running

[rstella]

I have a Volvo penta 5,7 regal. I ran into a muddy low area in a river and had to raise my transom and power out. Doing this I sucked up a lot of mud. When I powered away the temp gauge read very cool and then ran back up to about 170 where it normally runs at. The next week put the boat in the water and the alarm went off that it was overheating and then wouldn't restart. Got the boat home and my marina told me to flush out all the cooling lines which I did and also charged complete sea water pump and thermostat. Know when I take the boat out the temp runs about 160 but when I accelerate the temp goes up to about 175 and then comes back down after a few minutes of running. What does anyone think will make it do this because it never did it before I had the problem. What else should I try? Thanks Bob

 

[gotsea]

Thermos opening and closing as they should