15 hp Mercury still not right!

[pwmullins]

This is to further my previous post re same engine. I totally rebuilt carb with a kit and it started fine. Took it out for a test run and at high speed it ran good. 2 weeks later took it out and ran for about 30 minutes and when I throttled down to idle it cut out. Started again, but when I started to turn the throttle at the low end, it stopped. Got it started and "milked" throttle until I could get it up on plane and it ran good, just won't run at low rpm's . Stumped! Any of you small engine gurus experience this . Could it be sucking air at the connections? Help Please.