Did you hook it up the in right direction? I have it on all 3 of my units and none of the pumps have a problem. I can put my finger on the end of clear tubing and you can feel the suction. One can even hear and see the suction.Onecoolair- I purchased the same venturi that you are showing in your link- 3/4 inch- to use on my mermaid ac. I haven't hooked it up yet, because when I tested it on a garden hose it created a lot of back pressure. I'm worried it will over burden the water pump. Does your pump have to work overtime now to support the back pressure. Also, the venturi didn't seem to create much suction.
I guess I need to take a close up picture on how mine are installed. Must remember next time at boat. I then will post pics. Hopefully that will help.
In fact right before I left the boat this morning I had both units in the main salloon opened up. Just to do a quick inspection And So I could poor some Pine o pine into the pans and let the suction tubes suck up a little of the disinfectant just before I shut things down for the week. I also poured some in the bilge areas shower drain and shower sump. Makes the boat smell really nice and kills any mold that may try to grow from any left over moisture. I should have taken the time to pour some in the all raw water strainers too. But wanted to get back home and to work. Oh well can do that next week....