mercury outboard miss fire

[challengersrt8]

I have a 1997 mercury 115hp serial # og464835 the # 3&4 cylinders will not fire at low rpm.we cleaned the carburetors but did not help. may have missed something. you can spray gas in the carb and they will fire. the float bowls have gas in them . you can stick a rag in them and it makes them fire. what am I missing? what could it be? thanks for any help this boat was doing this when we got it. the 2 carburetor's on top have adjustment screws. the bottom 2 do not. is this right? has someone changed them and mixed them up.

[OldTimer57]

Did you clean the carbs carefully, making sure you got cleaner to flow through every single passage? There are tiny holes that have to be open, and letting a motor sit until the carbs are dry can easily plug small openings... I would clean them one at a time, again, and use a carb cleaner with a small spray tube. Hit every opening you see. Watch the needle/seats in each carb. Make sure you didn't bend a float so that it shuts fuel off too soon (there is a measurement given in the service manual normally). Etc.

[challengersrt8]

Thanks for your help old-timer. we did clean them very good. used compressed air with cleaner. set the floats at 9/16. are the 2 top carburetors the only ones with adjustments. The bottom 2 don't have adjustments. I was thinking someone may have been working on it before we got it. The carbs look new. would a crank trigger do this? thank you very much

[JOE54]

sir this engine only idles on the top 2 cyls/ 3 and 4 have no air screws was designed this way since 1987 known as the 2+2 4cyl JOE

[challengersrt8]

Thank you joe that helps me understand it.

[JOE54]

thought so also that engine needs to be in lake to make adjustments to idle and carbs they are finicky and run very lean at idle good luck