Very quick mercury 1985 9.8hp question

[mercuk]

Hi to all,

Just a very simple and easy question for all you mercury guru's out there. I rebuilt the carb on a mercury 1985 9.8 hp and got the idle screw pretty damn close. It stops, starts and accelerates smoothly however occasionally when I try to start it, she will backfire once then fire up after a few attempts.


My question is what should I do lean out the carb a little (because of backfire) or richen it up a bit. I know its pretty close becasue it idles o.k and accelerates well when under load.

Any suggestions would be VERY much appreciated from a u.k based Mercury enthusiast lol. Anyway thanks in advance to all those that try to help me out.

 

[impatico]

Re: Very quick mercury 1985 9.8hp question

did u tune it in gear in a barrel at idle?

 

[mercuk]

Re: Very quick mercury 1985 9.8hp question

did u tune it in gear in a barrel at idle?

Yes I did. The strangest thing happened as well whilst performing this task.... You would put the hood back on and the engine would drop a couple hundred rpm's??!!
Is this possibly related to the back fire on start up?!!

Anyway like I said, it ran o.k and accelerated smoothly etc, I just think it might need very minor adjustment like 1/8 turn or something because like I said, its pretty damn close.... But which way....... Hmmmmnn....

 

[woodsyfeller]

Re: Very quick mercury 1985 9.8hp question

The barrel will cause the engine to rebreath its exhaust so there isnt as much oxygen getting to carbs the issue is heightened when the cover is put on.

As to adjusting the needle valve Im guessing righty tighty (clockwise) will lean out the fuel because its seating the needle valve closer to the valve seat.

 

[mercuk]

Re: Very quick mercury 1985 9.8hp question

Thanks for the replies. Yes I would agree clockways would lean out the mixture. However is this what I need when there is a slight backfire on start up??!! I am right to presume the backfire is just unburnt fuel being ignited due to an over rich mixture?! Any suggesions?!!

 

[mercuk]

Re: Very quick mercury 1985 9.8hp question

Bump to the top...

Someone out there has got to help decide if its running a bit rich or lean... Its close real close and performs nearly flawlessly but a bit of a bugger to start when warm and back fires once before it does..

Anyone please?!1

 

[mercuk]

Re: Very quick mercury 1985 9.8hp question

Anyone??!!! Too rich or Too lean??!! any help please>!!