your problem doesn't so much sound like a lack of serratus, more just a lack of muscle in general. Only squatting 130lbs is a dead giveaway.
You only really need to do specific work for your serratus if you have some kind of shoulder issue, such as winged scapulae. I'm not saying to stop doing the serratus work, as it'll keep your shoulders healthy, but fixating on it will detract from the big picture, which is to develop muscle all over.
If you are pressing overhead, and using dumbells for your chest work then your serratus'll develop just fine along with the rest of you. If you really want to work it on its own, try dumbell protractions and the "serratus punch," both of those will work better than shoulder raises on the smith, as the smith removes the stabilising component, which is pretty much what your serratus does. Another little fancy trick you can try is on your last set of overhead presses, try and bang out a load of partials in the top position. In other words, just lower the bar a couple of inches from the top and press it up again. Do that until you feel like your eyes are going to bleed. That'll get your serratus working.
I understand where you're coming from though, a well developed serratus looks totally awesome, but getting a good looking serratus is more about having a muscular physique in general and low bodyfat. It's just too small a muscle for you to waste time doing loads of different exercises for. It just sort of takes care of itself as you get bigger.
So to summarise: don't worry too much about your serratus. Just get big and strong and you'll have an awesome serratus without having to worry too much about it.