Cooking a turkey takes around 20 minutes per lb so to cook a 25 lb turkey it would take 500 minutes.
At 500 minutes it would take around 8 and half hours to fully cook a 25 lb turkey so always get the turkey ready to cook as soon as possible before it's ready to be cooked and served because it will take almost the whole day for the 25 lb turkey to cook.
When a turkey is fully cooked the internal temperature of the turkey should be at least 165 F.