Low idle issues

I have a 2015 mercury 30 hp efi 4 stroke, I bought brand new last year. I don't run it all that often except during the fall for waterfowl hunting. The last time I ran it was in June and it ran perfectly, filled the tank after using it and added stabilizer. Now I get ready to take it out and I cant get it to stay running unless I use the throttle only button and turning the throttle up to roughly half to three quarters. Even after letting it warm up, i'll try to slowly back down the rpms and it will kill out between 1/4-1/2 throttle. Any help would be greatly appreciated. Thank you.

see if its running on all cylinders, you may have a fouled spark plug