The needles may have been over tightened at one time deforming their seats in the carb but that’s why they are adjustable, so you can dial it in. On these carbs, the high speed needle does affect fuel flow a small amount to the low speed circuit to so jumping back and forth adjusting the needles should give satisfactory results. The high speed needle may want to be on the rich side a bit to help the motors low speed running and coming off idle.
Throttle synchronisation has to be spot on for these motors to run right as does good compression for them to idle right down. Any air leaking thru worn bushings on the carbs butterfly shaft will also affect the idle.
Here’s some more info on them at this link and a parts PDF.
http://www.outboard-boat-motor-repair.c … cedure.htm
