For extremely hot water, you will need to change both thermostats on your heater. Even if the problem is caused by a single thermostat, it is recommended you change the two thermostats since they are affordable.
Before changing the current thermostat, it is advised that you purchase a new one of the same brand. If you can’t find such an item, look for a suitable replacement from another manufacturer.
Remember to add a non-contact voltage tester and screwdrivers on your list.