Carbs????? or=?????????

[Boat Doctor1]

Merc 4 cyl.- 100 hp. 4 carbs. When running @ idle- indicates a = lean condition- Cannot adjust out-carbs been throughly cleaned & new kits installed. Did same before cleaning all ! Firing on all cylinders.all ok there. This system has the external oiler on side of engine too-serial # = B376687 I am curious as to if something is stopping up a fuel line to the carb/s?? If fuel is induced while running - rpm picks up as expected .Runs fine - after carb s 2 indicate lean again= as lean in cylinder-- anyone experience this before??

 

[yzf125]

Without knowing all the details, my first thoughts are an air leak somewhere in or around the intake manifolds / carbs ? Could be alot of things but I would start there.

 

[Boat Doctor1]

Thanx i will go run it again & spray some carb cleaner around intake & carb mounting areas.

 

[Boat Doctor1]

Ok = did that no differences at all. Although I am seeing all 4 cylinders fire = with the neon spark testers- I believe now =maybe? there is an ignition problem on this engine -yet all 4 sparks are looking good- This engine acts like it has a"Lean" condition on 2 cylinders - adjacent to each other! Yet no differences made with carb cleaner or raw fuel put near any carb/ blocla surfaces. Above a fast idle -maybe 2000 rpm? all works as norman.Scratching my head on this one!!