Joel,
Think of this first pork butt experience as an excuse to try another one this weekend.
Using the already provided information will really help you make excellent pork the second time around. I would also keep a log (I use the one from this site) and keep track of what works and does not work for you. My cooking is much more consistent because I have kept logs of most of my cooks and can see what I did right and wrong.
As for the temps, I used to go by internal but now it's all about the probe tender method. I do use a meat probe to watch the temps so I know when to start checking for tender. I've had tender butts at 190-195, and I have had to go to 200 on others, so like others have said there is now set temp for when to take it off.
Now as for your thermapen reading 180, I can only think of 2 things that caused this.
First, check your calibration using the method below. If it does not read correctly, call up Thermoworks and ask for it to be replaced or fixed. They are very helpful people. You may not really need it for pork butts, but you spent $100 on it, so you want it accurate.
Second, at what point did you add the cool water to the pan ? I once added cool water to a pan and it took awhile for the cook to recover. The meat actually dropped in temp (it was 1 butt on a the bottom rack). Maybe you actually got up to a higher internal temp but by adding the water slowed things down and reversed the temps a bit. This is an example of why keeping a log helps, I noted that I added cool tap water and realized NEVER to do that again.
I am now starting to cook without water on butts, but always add hot water so that you are not using up the heat to warm water. Water is great when you are learning as it evens out the temperature range.
Checking thermometer accuracy:
Performing an Ice Bath Test
An ice bath test is the easiest way to test the accuracy of any thermometer, but only if it is created properly.
Internet videos notwithstanding, an ice bath is NOT just a glass of Ice water.*
Follow this four step process carefully to create a proper ice bath:
Step 1: Fill a large glass to the very top with ice (crushed ice is preferred but not required).
Step 2: Slowly add very cold water until the water reaches about one half inch (1 centimeter) below the top of the ice.
Note: If the ice floats up off the very bottom of the glass at all, the ice bath may be warmer than 32°F (0°C). Pour off any excess water.
Step 3: Gently stir the ice mixture and let it sit for a minute or two.
Step 4: Insert the probe of the thermometer being tested about 2 inches (5 centimeters) into the ice mixture and gently stir while you take your reading.
*In our experience, an improperly made ice bath can be off the ice point as much as 15°F (8°C).
Note: Be sure to keep stirring gently. If the tip of your thermometer probe comes to rest against a chunk of ice, it will show a temperature below the ice point and if it comes to rest against the sides or bottom of the glass, it may read higher. Your thermometer will continue to drop till it reads close to 32°F.
Performing a Boiling Water Test
Boiling water tests are even trickier to perform correctly than ice baths. Water boils at 212°F (100°C) at sea level but only at sea level. The change in atmospheric pressure at elevations above or below sea level alters the temperature at which water boils. We provide a Boiling Point Calculator that will walk you through the steps to know what the current temperature of boiling water is at your location. You can find the online calculator at
www.thermoworks.com/boilingpointcalculator. Once you have the target temperature written down, you are ready to begin your boiling water test:
Place 4 inches of water on the stove top, once a rolling boil begins insert the probe 2 inches down. The read out will rise until it reaches close to the temperature given to you by the calculator.
If your thermometer is reading correctly in either or both of these tests it will also be accurate over its entire range of temperatures in any food or liquid.