Conventional thinking is 1.5 to 2 hours per pound, looks like you got one a little over 7lb, my guess it will take about 10 hours at 250. If you want to speed that up, when it gets to 165-170 internal temp, you can wrap it in foil with a little apple juice.
If you don't want to wrap it, it will hit what is called the "stall" around 155-170 and it will sit there for a couple hours or so, don't worry about that it's completely normal, that's when all the magic is happening inside the meat, the fat is rendering. It will eventually come out of it and the temps will begin to climb again.
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