question on old merc carb

[mla2ofus]

I've been resurrecting an old 110 ('64-'65) and have had trouble getting a smooth idle. Took carb apart first thing and it was super clean inside. Finished all the other things needing done and stuck it in the test tank. Runs fine at high speed but couldn't get a smooth idle. Decided to take it apart again and soak it in carb cleaner. Just took it out and was cleaning it up for reassembly when I noticed this small hole shown in the pic. Other pic is to show the hole is open to atmosphere but is on the vacuum side of throttle butterfly. What gives here???? Is this something a plug may have fallen out of? I can't see any threads in the hole. Doesn't make sense to me to have an open hole there. Could someone enlighten me???
TIA,
Mike

 

[will941s]

Re: question on old merc carb

I have no clue either, but is it possible to put your finger over it while its running? Or find someway to plug it while you run the motor and see if it helps the idle, something that you can remove.

 

[mla2ofus]

Re: question on old merc carb

I have no clue either, but is it possible to put your finger over it while its running? Or find someway to plug it while you run the motor and see if it helps the idle, something that you can remove.

Well, if someone doesn't know I'll tap it w/ #6 or #8 and put a short screw in it and see what happens. The hole is behind the carb mounting stud when installed, so if this doesn't work I can remove the carb again and take the screw back out. I've never seen a carb w/ a hole like that that isn't a vacuum port for some reason or another.
Thanks for the help, I'm in no rush on this so I'll wait awhile to see if someone more knowledgable can answer.
Mike