What happens if the thermostat is removed of the engine?

The first thing you will notice is that it will take longer for the engine to warm up to normal operating temps, then you will see more of a swing in operating temperatures for different operations and ambient air temparatures. If it is very cold outside you may see the engine overcool when not working hard. Thus will be more of a nuisance than anything unless it's a diesel, then you may actually overcool the engine and cause excessive wear and tear on the engine and may cause fuel oil dilution ( diesel in your oil). Diesel's need a water temp above 140 degrees f when operating due to the high flashpoint (140f) of diesel compared to gasoline.