Use a thermostat. Without a thermostat, the water can run thru the radiator too quickly to remove enough heat ... so the engine runs hotter. Use somewhere between 180 and 195 ºF thermostat at all times. Using a thermostat will also speed up the time it takes to get to operating temp.
Engine
oil temp and water temp should be equal when moving (80 to 90 ºC)
I assume that your gauges are accurate?????