Just finished carb rebuilds and link and sync. Engine runs great throttled up, just coughs while in gear idling. Anyone have an idea of what it may be.
Thanks to all!

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.

Only problem on this one is the carbs are all fixed jet and no adjustment screws.

how did ya set idle timing? on tha hose or in gear in tha water? all bleed lines good and fittings (tha one-way ones) workin' like they should?

I set it on the hose. I'll try to get it back in the water and check it.
Thanks

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

Many times that idle cough is caused by the idle timing module.

absolutely... first thing ta float test.. gettin' a "little" forgetful!

Thanks guys got rid of the module a while back. Hopefully get time the next few days to check and set the timing on the water.

Finally had some time to work on it. I had a switchbox working intermittently and losing a cylinder at times. Still sounds like a hot rod idling, but not coughing or dying anymore.