1991 90HP Backfire

[Shrbnd]

The outboard seems to be backfiring when I am starting it up whether hot or cold. It seems to miss, backfire which sounds like high pressure air being squeezed out a balloon, and stalls out. There seems to be blue exhaust coming out of the air silencer. It starts back up and seems to run fine. Any idea what might be causing this? Any cause for concern?

[boats.net]

Sounds like it too lean, dirty carbs or air leak in intake manifold.