I kind of had a similar question lately. With rising summer water temps in the bay and barnacles probably growing around my water intakes, my engines have been running closer to 200 while cruising. The alarm on one came on after coming back off plane recently and I let it idle. Temp came back down under 200, but alarm kept going for several minutes after. Is that the sender switch that's hanging up or is there a timer built into the alarm circuit?
And these are closed cooling engines, which should be why they run warmer.