radiator fan switch

It stays near 195 because the thermostat will restrict the flow and hold the temperature. that was my point if you get switch that turns off below 195F then once it comes on it will run constantly.

On many vehicles that have a temp gauge the gauge is designed to not move much in the normal operating range so you don't observe the fluctuating when the fan goes on and off. The needle on the gauge moves quite a bit from something like 150-190 and then it moves very little from 190-220 and if the temp gets above 220 the needle starts to move upward pretty quickly. You are going to need a more sophisticated control system than a switch with a single upper and lower limit. You don't want it so the fan comes on for 5 seconds and off for five seconds - on and off constantly. That isn't good for longevity of the switch or fan. If there good flow of air when the airboat is moving it may not need the fan except when it is idling. If you can get a switch that turns off at exactly 195 it may run constantly at idle but once you get moving the extra cooling may drop the temp enough to shut it off.

-jim