If it's 170, in my opinion it isn't close to done...so you should be able to tell. I haven't looked around at what people say on this forum about when to pull off butts, so I may get blasted for this but...
I feel like the worst thing you can do to a boston butt is to pull it too soon. Due to the fat layer on top (hopefully on top), they can take a bit of overcooking. If the bone doesn't yield at all, it's not done. If it yields some, then you can wrap it in aluminum foil and put it in a cooler for 1-4 hours. I've found that helps the end product if your going to do pulled pork.
This is all opinion, but isn't all bbq...