Loc: cedar creek lake
Sounds like you may have a lean "sneeze"/ cough. You need to figure out which carb(s) is causing it. Plenty of you tube videos on how to adjust air mix screws on the carbs. One or more needs to be turned out. Only turn about a 1/4 turn at a time. Do this in the water or in a test tank.
when ya do don't even worry 'bout "numbers and or rpm"... set tha timin'/rpm (in gear) ta whatever you and tha motor are happy with.... idle timin' numbers in "tha book" don't always hold true to a lotta motors (V6 mercs)... mainly justa ball park deal......gl