Hard to see the coat, but that may well be a "purebred" Labrador. Might even be registered, believe-it-or-not. The breed standard calls for a 60-80lb dawg, but there's a lot of "breeders" out there who have no clue what the breed standard says and/or don't care. I've seen adult Labs in ideal condition run from 50lbs to 110lbs. I've heard about Labs at 140 (who would want to hunt with a moose like that??) but never seen one.
If it's a cross, I'd guess 1/2 Lab, and 1/2 Great Pyrenees (sp) like some of the others guessed. Ryan, do you know what the dog IS? are you playing with us? :lol: