For one, teflon tape on fuel lines can be a problem waiting to happen. You'll notice that the tape is frayed looking on the outside of the inlet plumbing in your pic. You can imagine that those frayed ends could let go and fall off into the bilge right? Well, they can also fray on the end inside the pump from being cut in the threads. If that happens it can get inside the pump or line and be passed into the carb if there is no filter between the pump and carbs. From there they can do anything from sticking a needle and seat to clogging a main jet. So from that standpoint, you might want to look into using teflon paste or some Permatex 1B on your fittings in place of the teflon tape.
As for why yours is leaking... It might not be tight enough, or perhaps the fittings you have may not have a good enough taper to seal properly. It's hard to tell from a picture. Assuming the pump is new and the threads were in good shape, you've already checked for cracks in the housing and all is well, I'd change to teflon paste or Permatex 1B and use a little more torque. if that fails, change out the fittings, again using teflon paste of Permatex 1B.
Good luck,
Chris