first full turkey

[oregon redneck]

Good Evening smokers!
First time poster here and have a question. I smoked a 18lb turkey this morning. planned on about a 12 hour smoke/ cook. Put it in at 4:15 AM with 15 biscuits. Temp was set on machine at medium to high and gauge read about 225. At 12:30 checked things out and internal temperature on meat was at 150 degrees already.
Based off what I have read on this forum most turkeys take about 30-45 minutes per pound so it should have been about a 12-13 hour cook. Did I miss something? Any ideas. Its a bone stock new original Bradley with the smoke front face. No modifications.
I look forward to any advice and have appreciated all the great reading preparing for my first major smoke.

[beefmann]

last  turkey i had done took just under 10 hours and it was a 21 lb turkey which means closer to 30 mins a lb...my box temp was at 225 and took the turkey to 180,,,, i would still go by temp over time any day there are a  lot of out side conditions that  come into play,,, like  how much moisture the turkey has.. moisture in the cabinet , wind, and out side temp... so go with it and pull your turkey  some where between 170 and 180