Ok so here is my issue here. I have a 2002 cobalt 262 with Volvo 8.1 liter 502 I believe. While taking it out for the first time this year the impeller failed and boat got hot. Real hot. It melted the exhaust boots on the engine and burn the paint off exhaust pipes. I had my mechanic replace all parts of the cooling system. Took it back out and it ran about 180-185 on plane but when idle it got hot again and it shut it down. Took it back and he said prolly a blockage. He back flushed it all. Again and I took it back out and then it would climb to about 190 and stay there no matter on plane or idling. So I took it back to him and he took all hoses off and hooked it up to hose to make sure water is pumping and it was. So all aspects of cooling system are working however boat still gets up to 190 degrees when it should be and used to run 170-175. Next he is going to try a compression test but doesn’t think it’s in the engine because engine runs fine doesn’t miss a beat it just runs too hot all the time. Looking for suggestions on why this could be. Thanks