Merc 9.8 idle

[WOJO 1]

This little motor has a rough inconsistent idle. If the check valves in the fuel pump were bad would this casue a rough idle or some other symptom? I did replace the gasket and diaghram but not the check valves and don't want to unless it will help. Any help would be great.

 

[crem1]

Re: Merc 9.8 idle

It could be any number of things. How does it run at higher RPM's? Could be carburator problems(needs cleaning)

 

[WOJO 1]

Re: Merc 9.8 idle

crem1, it does run a lot better at higher RPM. I already did the carb. It was removed and completly cleaned, replacing the gaskets and needle and seat. The only thing that did not get changed was the float and the idle/mix screw. I am now messing with the float level adjustments trying to get it to idle better. Seems that when the engine is cold you would choke to start. If I choke it and pull the cord once, there is a good amount of fuel that exits the carb then it starts without the choke off. Seems to me that this means there is to much fuel. Wouldn't you think.

 

[crem1]

Re: Merc 9.8 idle

Did you actually take all the items out of the carb and then soak them in organic solvent for a day? Otherwise idle adjustment screw is in order

 

[WOJO 1]

Re: Merc 9.8 idle

Did you actually take all the items out of the carb and then soak them in organic solvent for a day? Otherwise idle adjustment screw is in order

Nope just carb cleaner and compressed air.
Where would one find an idle mixture screw for this motor? I have searched high and low and can find just about everything but the idle mixture screw.

 

[crem1]

Re: Merc 9.8 idle

You have to let the carb and all the parts soak for at least 1day to remove all the gum and gunk from the surfaces
Are we talking about 1968 MERC 110 9.8 HP engine?

 

[WOJO 1]

Re: Merc 9.8 idle

Are we talking about 1968 MERC 110 9.8 HP engine?

Yes we are.

 

[crem1]

Re: Merc 9.8 idle

This is an integrated unit where the fuel pump is part of the carburator. The idle adjustment screw should be in front of you as you are looking at it.(idle restriction tube and idle adjustment)
Take a picture of your unit if you have ongoing problems

 

[WOJO 1]

Re: Merc 9.8 idle

The fuel pump is not integrated wit the carb on this one. It sits right next to it.
I guess on my other post I was not clear, I know where the idle screw is on the motor. But I can not find a replacement screw any where.

 

[crem1]

Re: Merc 9.8 idle

I don't know what you mean by a replacement screw. However the arrow on the return picture is the idle screw

 

[WOJO 1]

Re: Merc 9.8 idle

I don't know what you mean by a replacement screw.

A replacement screw. A new one. I have been unable to find a part number for a new idle/mixture screw. Would this be an item that would normally not go bad even if it was over tightened? I have no idea how this motor was handled before I got it.

 

[crem1]

Re: Merc 9.8 idle

Then you have a pressure type carburator if the fuel pump is not integrated. You might have to look for the whole carburator on e-bay, I don't think they would sell the screw by itself.