If running with no thermostat caused overheating then every vehicle should overheat without a thermostat and that doesn't happen. I have compared no thermosat, high flow thermostat, and standard thermostat. Engine temperature increased incrementally with each reduction in flow. It just isn't as simple as saying "the water doesn't have time to cool". I haven't heard a good explanation or analysis anywhere of why removing a thermostat can cause an engine to overheat.
