Sync carbs '97 Merc 125

Where are vacuum ports? Want to use 4 gauges to balance carbs. This 125ELPTO uses two carbs with low rpm's. Two have adjustable mix needles, and two have fixed. I have shop manual, but only shows mechanical linkage adjustment routine.
Engine running very well, but want to achieve best balance.
Any insights appreciated.

You don't balance carbs on outboards. If Mercury wanted the carbs balanced they would put it in the manual you only do the link and sync. Get the factory manual for your motor but if it is running good leave it alone. That is a motor that is very easy to screw up and very hard to get back to running good after it is messed up.

Flyingscott... thanks for the reply. I do have the factory manual. I'll take your word for the 1997 year 125 being easy to screw up, and I certainly will be most careful with adjustments.
I have to say that your statement that "you don't balance carbs on outboards" is a bit absolute sounding in opinion. I've seen a good many videos and tutorials on many different brands of multi-carb outboard engines where vacuum syncing carbs improved performance considerably. The individuals producing these helpful guides were very knowledgeable about outboard performance, and the balanced gauge readings and on water tests after adjustment were clear evidence of improved balance. As for a balance procedure not being in the manual: there would never have been a race boat or car built if they only used the "factory shop manual".

It's your motor do what you want I am not going to argue with you. I would suggest you ask the people in the videos for advice.

Only the 4 stroke outboards use carb balancing....