All,  I'm winterizing my boat myself for the first time,  in the water, and trying to figure the best way to winterize the AC system.  Yard did this in the past on the hard by pulling AF through the out port  with a pump but claimed i could use gravity to feed AF into system from that port. 
But I'm trying to finish in the water.  I tried to disconnect the water input hose and put it in a vat of anti freeze and have the AC pump do the work but it would not push anything through -  it appears that it needs the pressure of the water from outside to move the pump???   
So i took both input and output hoses off and blew air through the system as another member suggested.  I'm not sure this will do the job for the pump itself tho.

Any thoughts on best approach would be welcome.   Thanks, Bob