I also have this same exact problem on my 60 horse. I may attempt to adjust the idle next time i'm out and see what it does. The guy that got my motor running and rebuilt the carbs showed me a single screw on the starboard side that he said adjusts the idle. I'll post up any results. It runs at idle great on the muffs but can be a real pain when i try to idle onto the trailer and it dies and won't start, i've ran up on my trailer sideways twice now because it has happened.