7 months old seems pretty old for that kind of mouthing.
Our Bouvier, at about 10-14 weeks was extremely mouthy f when he was highly aroused.This usually happened outside.
What worked very quickly was: making sure he was on a leash at times he was likely to exhibit the mouthy behavior, and pounding a stake into the ground. I could almost predict exactly when it was going to start, and I'd make sure we were near the stake. As soon as he started, I yelped LOUDLY, slipped the leash over the stake and walked out of range. I stood away from him, very still, for a minute or so, and then walked back to continue to play like nothing happened. After a couple of weeks of doing this very consistently he stopped. I was like, 100% consistent though. Also, when inside, I would slip the leash over a banister, or whatever was nearby to allow me to walk out of range.
He dragged a leash inside for a long time (for many reasons). I was amazed at how quickly his mouthy behavior extinguished by simply withdrawing all attention.
Again, the pup you are working with is much older, and I don't know if the above approach would work. With my Bouv, it was all a result of a high state of arousal and not knowing another outlet.