How long for a 7.5 lb cure 81 ham?

Until you hit 165ish, maybe 5-6 hrs???

What is a 81 ham?

Cure 81 is Hormel (I think) upper end ham. It is "ham in natural juices" so its the real deal ham and no processing, but it is already cooked. I would be careful with leaving it on to long, as even with lower temps to get a smoke flavor, the ham can become very salty from the loss of moisture. I just smoked a 1/2 ham with apple and then sliced very thin and it lasted 4 days, and it was supposed to be just for lunches.