9.9 stalls at idle

[mattfish11]

I just had my fuel pump replaced for my Mariner 1989 Mercury 9.9 motor (serial #OB388303)...

I got it back and I started running it... It runs really well when I give it gas, but when I take it back to idle - it just dies... Do I need to increase the fuel flow when idling? How do I do this?

Any suggestions? Thanks!

Matty Kling

 

[Barnacle_Bill]

Re: 9.9 stalls at idle


When is the last time you did a de-carb? (see FAQs) and a linc & sync? (check your manual)

 

[mattfish11]

Re: 9.9 stalls at idle

The carbs were soaked in solvent to remove any excess carbon... They (certified Merc mechanics) cleaned out the carbs, and replaced the fuel pump.

I figured I would see if there was an easy fix for this on this board before having them look at it again for $110 an hour!

Thanks!

 

[Barnacle_Bill]

Re: 9.9 stalls at idle

Then it may be as simple as adjusting the idle. I don't have a manual for that motor or I would look it up for you.

 

[mattfish11]

Re: 9.9 stalls at idle

I don't have the manual either...

I know there is an adjustment screw on the motor itself, it's a brass (i think) screww that looks like it adjusts the carbs.. I don't know if this is what I have to mess with (caus i don't want to mess with it)...

I don't know how to "adjust the idle"...

 

[vgiljebr]

Re: 9.9 stalls at idle

I just had that problem on my 89 mercury 9.9, same engine as yours.

The idle adjustment screw is behind the black carburator cover. There should be a black plug you can remove to get access to the idle adjustment screw. I just did this using a Seloc manual and the correct procedure is as follows.

"Run the motor in forward app 700-800rpm in a tank or 6-700 rpm on a boat. "Turn the adjusting screw counter clockwise until the engine fires unevenly from the mixture being too rich. Now (before it stalls) begin to turn the screw clockwise and rpm will begin to increase. Coninue turning the adjusting screw until the mixture is so lean that the rpm begins to drop and the engine begins to misfire. Set the adjusting screw halfway between the rich and lean points. It is recommended to have the mixture set slightly on the rich side, rather than too lean."

I havent experienced much stalling at idle after using this procedure.