Originally Posted by Stinger390X (Post 3382093)

No engine should run without a thermostat. All engines which produce horsepower need to operate at "operating temperature" for optimum performance.
In a boat the steady flow of water will cause the engine to run cooler than normal which may cause loss of power, sludged oil or fouled plugs and a host of other conditions.
In an automobile with a radiator, if an engine operates without a thermostat it might even overheat! you ask how...it's because the coolant does not stay in the radiator long enought for ambient air to cool it so you are sending hot water back into the block. In a boat you are probably using sea water which is already cool causing lower than normal engine temps.
Hope that helps you inquirey?