1989 Mercury 115hp 2 Stroke Outboard won’t hold idle

[Asm4]

I have a 1989 115hp 2 stroke mercury outboard with and advanced injection system. The engine will start and stay on when rpm is raised but when left in neutral or idle forward/reverse it cuts out. In truth it’s been a while since the carburetors were cleaned. Our original mechanic 2 decades ago said there was a problem with the float valve but said not to touch it as it would cause more damage getting to it than just leaving it be. Is the fix as simple as cleaning them or is there something else to adjust/fix/replace?

 

[racerone]

It is not always the carburetors.----Do the trouble shooting.----Do you replace the water pump impeller every 5 years ?

 

[Droid]

Isn't that the beast that idles on just 1 carburetor/2 cylinders?

 

[racerone]

The motor has 4 carburetors.------Idles on the top 2 cylinders.-----Bottom 2 carburetors kick in at 1800 RPM.

 

[Asm4]

It is not always the carburetors.----Do the trouble shooting.----Do you replace the water pump impeller every 5 years ?

I believe the impeller is 3 years old

 

[racerone]

Step #1 is always a compression test.--Post the actual values here.-----Need to establish overall condition of the motor.---Just like going to your medic.----Most will check blood pressure before talking details !