Assume no mixture adjustments, EPA outlawed these 10-15 years ago. Just the slightest amount of corrosion in the jets or film will cause these kind of problems. Have a set of numbered drills, #1 to #80 size, find the right one to clean that hole, better not enlarge it. Go to any dealer, will tell you, you need a new carb. Are you using E10 in this machine? Sure corrodes the insides of those jets. At one time, can't remember, don't want to, we could only buy E10, Mercury Outboard screamed the loudest, as well as other manufacturers of outboards and small engines, ATV's, snowmobiles. So we could then buy 91 octane, ethanol free, now some stations are selling it in 89 octane. It sure made one hell of a mess with my 88 Supra, you could have heard me cussing from here. Some of the newer engines claim to be E10 compatible. My Volvo I/O boat has a sign by the gas cap, do not use ethanol, but the only place I found this sign on any of my old stuff. Fuel stabilizer does not work with ethanol.