I recently messed up a pork butt and instead of juicy and tender, it was dry and hard. Not very good. The internal temp was 200 degrees in 5:30, so I thought my digital thermometer was broken. I knew that you are suppose to cook a butt for 1:30 to 2:00 per pound, so I let the butt sit for another 7 hours. Needless to say, not a good butt. The only conclusion I could come up with was the dome thermometer was off. Therefore, I calibrated it to boiling water and sure enough, the dome thermometer was 150 degrees off. My questions are: 1. Why would this happen? 2. My thermometer needle now starts between 100 and 200, see below pic. Is this ok?