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  1. #1
    Join Date
    Apr 2019
    Location
    West Linn, Oregon
    Posts
    8

    Default 1985 Mercury 18 XD fast idle adjustment

    Hey everyone,
    I have a new to me 1985 Mercury 18 hp (XD) (Serial A115159). Engine runs well but at low idle is a little rough.

    I see the fast idle adjustment is under the choke face plate (highlighted in yellow). I want to make sure that I am proceeding correctly to adjust the fast idle before I screw something up. I probed the face plate over the weekend and the cover seems to be a sticker. Can anyone confirm that I am supposed to remove the sticker to get to the fast idle adjustment knob, or refer me to a better procedure to do this?

    Thank you, I appreciate any feedback given.



    Click image for larger version. 

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  2. #2

    Default Re: 1985 Mercury 18 XD fast idle adjustment

    That screw in the carb is the low speed fuel mix not the idle speed screw. Adjust it 1/8" at a time to see if you can get the idle smoother.

  3. #3
    Join Date
    Sep 2010
    Posts
    17,516

    Default Re: 1985 Mercury 18 XD fast idle adjustment

    The knob in yellow adjust idle timing.-----Screw item 16 on front / upper part of the carburetor adjust slow speed mixture.----There are lots if items identified as #16 ( carburetor repair kit ) ----I think it is obvious as to what to adjust for idle mixture here.

  4. #4

    Default Re: 1985 Mercury 18 XD fast idle adjustment

    Nothing in that pic adjusts the idle!!! That knob in yellow is an adjustment for the idle for cold starts only. #40 in this pic is your idle screw http://www.marineengine.com/parts/me...mercury-manual
    Last edited by flyingscott; 09-11-2019 at 04:23 PM.

  5. #5
    Join Date
    Sep 2010
    Posts
    17,516

    Default Re: 1985 Mercury 18 XD fast idle adjustment

    The picture in post #1 does show the mixture screw for low speed performance.----The poster says that idle is a " bit rough " and adjusting the mixture may help smooth it out.

  6. #6

    Default Re: 1985 Mercury 18 XD fast idle adjustment

    Post #2

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