Tough to say.
First of all, since you have been marinating it, it will cook quicker.
I assume it is a full blown loin and not one of those little tenderloins.....in which case it ought to be around 10-12 pounds??
I'm guessing less than two hours low and slow.........less if you are cooking over hot coals (which I think is fine for this cut).
I like pork loin medium rare.......around 135F......but this makes some people squeamish. Good thing though, is you can toss the slices on a hot grill and finish them if you like.