I generally cook butts at 275-285. As a rule of thumb 1:15-1:30 hour per pound, but each butt will be different. You are shooting for an internal temp of 200-205. If you probe test for tenderness, be sure to check several different part of the butt. The biggest key is the rest after cooking. Foil it tight & put in a dry cooler then pack the rest of the cooler with old towels or newspaper & let it rest for at least 1 hour. Go longer if you can. It will still be too hot to handle after 5-6 hours if wrapped & packed properly. Bone in is the way to go. Pull as soon as you can handle the meat after resting. I use a cheap pair of cotton work gloves covered with nitrile gloves to pull hot pork. Save those juices in the foil. You can separate the fat & use the rest when reheating.
Jim Sewell -- GBA Master Judge, Contest Rep & GBA Webmaster