I had an engine overheat in a 1985 M25 Universal with 600 hours presumably from a bad thermostat that stuck shut. I do not know the duration or extent of temperature rise in coolent because the boat was on charter. Head cover, injector nozzles and basically anything attached to top of engine shows evidence of heat discoloration as original gold paint was essentially burnt off during incident. Oil in crankcase smelled acrid and burnt. Has anyone had a similar experience with this type of overheat where coolent was present, but did not circulate and caused metal discoloration and if so, what was the outcome on engine condition or performace? The engine seems to run fine, but have not yet checked compression.