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Johnson 48hp rough idle & smokes......normal?

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  • Johnson 48hp rough idle & smokes......normal?

    My 1985 Johnson 48hp 2 cylinder always has shaken a little in idle and smoked. The dealer I bought it from last year said this is normal for a 2 cylinder Johnson. Is this true? Seems to run good otherwise. Bob
    1990 Bayliner Capri 1850 BR - GM 3.0L Mercruiser Alpha One Sterndrive.


  • #2
    Re: Johnson 48hp rough idle & smokes......normal?

    He sounds to be shooting pretty straight with you.The two cylinder John/Rudes don't idle real smoothe.Keep fresh Champion plugs in it each season and mix your fuel at exactly 50:1 using a BIA/TCW3 oil and fresh 87 octane fuel.A seasonal decarb will keep it running better as well.

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    • #3
      Re: Johnson 48hp rough idle & smokes......normal?

      Whats a seasonal decarb?ThanksBob
      1990 Bayliner Capri 1850 BR - GM 3.0L Mercruiser Alpha One Sterndrive.

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      • #4
        Re: Johnson 48hp rough idle & smokes......normal?

        There are several products available that can be either mixed in with your fuel tank or sprayed directly into the engines cylinders via sparkplug holes that will break up carbon deposits from piston ring grooves and piston heads.This will keep your engine ooperating more efficiently and prevent any excessive carbon related compression issues.You can visit the FAQ section of these forums for some good reading on the subject or perform a search on one of the various forums.

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        • #5
          Re: Johnson 48hp rough idle & smokes......normal?

          you run it through the carb. it will clean the gum and varnish off the reeds and remove carbon from the pistons and exaust. You can use decarb or sea foam, i prefer decarb, you can get it at napa they will have to order it, or most marine dealers have it or sea foam just follow the instructions. Or you can run b-12 in your gas that also helps.

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          • #6
            Re: Johnson 48hp rough idle & smokes......normal?

            Read this. http://www.iboats.com/cgi-bin/ubb/ul...;f=36;t=000016

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            • #7
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              Re: Johnson 48hp rough idle & smokes......normal?

              Great info, Thanks all!Bob
              1990 Bayliner Capri 1850 BR - GM 3.0L Mercruiser Alpha One Sterndrive.

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