1990 30Hp Two Stroke Yamaha - will not idle

I have a friend that owns a 1990 30 Hp Yamaha that refuses to idle. It will start with the engine at full throttle (out of gear of course) and when you lower the throttle arm slowly, it starts to sputter. At that point if you lower it anymore the engine will cut off. It sounds like a “carb” problem, but I would hate to take everything apart to find that it could be a simple adjustment. Any suggestions?

Probably one or more of the jets is clogged…pretty typical for those motors if they sit for a while with untreated gas in them.

that motor has 3 carbs
rarely do they ever need adjusting, unless you have a problem, then if you just fix the proble, no need to “adjust”
sounds like the idle circuits in the carbs are clogged
the engine gets fuel from a different passageway for more open throttle positions
you need a carb job