mag 18 isnt big enough for the monster skimmer?NEED HELP!!!

[Tarolisol]

Well i have the skimmer hooked up and have determined the mag 18 just wont cut it, Instead of the beckett sucking in air its sucking in air and spitting lots of water, i figure this is because the pump isnt spushing hard enough. Can anyone conquer? Also it can even push the bubbles into the larger tube. Can someone recomend a new pump, I would really really like it to be submersible, unless there is a way to put an external pump on without drilling my sump.