I'm having trouble cutting and pasting links to this site or, otherwise, I would send you a parts page from boats.net
As it is I will just have to say that you can pull up the diagram for:
TIMING BELT COVER + MOUNT CASE under the 90hp on boats.net.
Item 14 is a hose that appears to connect to a nipple at the case.
I'm not sure if this answers your question but thought I would point it out in case it's what you're looking for.
I will say that the bottom of the air box SHOULD have a drain of some kind to keep it from filling with condensate from oil vapors due to the crankcase being vented there. But I am not familiar with the 90A having never worked on one.
Good luck.