Maybe this has been posted before...but I've seen the Nautilus getting a bad rap lately!
I had a similar issue with poor suction while trying to winterize....because I emptied my first gallon of anti-freeze, started sucking air, and I lost the prime on my pump. I found that if I open the cold water low-point drain for a few seconds (with a bucket below it), the air would purge quickly and the pump would starting pulling again. For me it worked really well. I also learned to pour 2 gallons of anti-freeze into a bucket before I started....to make sure I didn't run low.