1988 mercury 90 2 stroke very fast idle, then stalls

Hello, I have a 1988 mercury 90 hp 2 stroke 3 cylinder outboard on my pontoon. Was running fine, until 2 weeks ago, took it off trailer, then it stalled, and could not get it started again. Got home, decarbed the motor, took apart and cleaned out the three carbs, put a new fuel filter on, new primer bulb and hose, some new fuel lines. It started right up, but the idle is very high, around 2100 rpm, and will stay like that until it eventually stalls. I am at my limits on what I know about this motor. I tried adjusting idle, adjusted screws on carbs, nothing. Idle may go down a little, but then it struggles to run and then stalls. Fresh fuel is in it. Any ideas? Thanks

You mention adjusting the idle and carbs, but did you do a full "link and sync"? This would cover everything from the carb butterflys closed/open positions, throttle linkage, idle screw, and fuel mixture screws. This should get your correct idle setting back and carbs adjusted properly since you've last touched them. Then go from there. If you have a full service manual for your motor it likelly has an in-depth explanation of how to do this very process and isn't too hard to do (I did one myself a week or so ago and resolved a fast idle issue)

I see it didn't have the high-idle issue initially. But, being that you mentioned taking the carbs out to clean them makes me wonder if the throttle linkages and carbs should be resyncd properly incase something moved during re-installation of the carbs.

At least you'll know you have your carbs set properly, so from there you can continue troubleshooting Spark/Air/Fuel (do the basics first, like testing plugs/no clogged air box or filter/no fuel line kinks or leaks)

..."cleaned out the three carbs"

Define how you did this.

Jeff