Ok so first off I had my 2005 40 mercury 3 cylinder
ported and bought some used 60 carbs which turned out to be 90 carbs. anyways spent a while trying to get it to run before trying actual 60 carbs that made it run perfect so went straight to boats.net and ordered the same part number carbs that made it run right well after I ordered them they sent me an email and said mercury superseded those carbs with a new carb and part number well the carbs i got in the mail are the same. My question is what is the difference between the 2. the difference I see is there is a screw of some sort in front of the idle air screw on the 60 but nothing in the 90's but a threaded hole. Any info on this would be awesome. Thanks guys