First of all, you NEED a thermostat if you have a UTH. UTH's can easily get up to 120 degrees, and when they fail, they fail on, meaning that they continue to get hotter and hotter rather than turning off. If you'd like I can look up twenty threads with pictures of severe burns caused by a UTH without a thermostat to prove this, but trust me you need one.

Also, what kind of thermometer are you using to measure temp? If you have an infrared or laser thermometer you can actually point it at a surface and it'll tell you what the temp is.