Non priming aerator pumps, any ideas are welcome

[freeheel4life]

So I've got to go on a long trip out of town for a customer.
Primary complaint is rear pumps won't prime. Boat is a 13 z3. Wondering who else has had this problem and what your solution was. I'm guessing that hose runs from outlets of pumps are running up too far and can't overcome and airbubble but as I am driving 4 hours one way to try and solve I would like to have a better handle on it than mere theory.
Mike any ideas?? Elevated?? Any other hard tank to bag gravity system thru this gen of z3s please chime in too. Strangest thing is first owner of boat never complained and I believe the only change between first and second owner is enzo sacs. Doesn't necessarily mean it wasn't happening before, first owner may not have noticed. Boat has only come to us for winterizations since it left so....
Believe his boat has the 1200 GPH pumps but will text him tomorrow to make sure.

[chpthril]

First thing to look at is the orientation of the pump outlet. The pump is likely positioned so that the outlet is slightly down from the body of the pump, which will trap air. The fix is to rotate the pump body to get the outlet so its uphill. Also want to make sure the outlet fitting (if an elbow) is also turned somewhat up and not down. This may be tougher done they said as we've come across some pumps glued into the ball valves by tige.

The next thing to look for is check valves. Tige has been fond of the bronze marine swing check valves. These have a habit of allowing upstream water left in the hose, to sit on top of the swing door, trapping air in the pump next time the boat is launched. Id suggest tossing these and going with a duck bill style check valve.