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Results 1 to 15 of 15
  1. #1
    Join Date
    Feb 2012
    Location
    Madison, WV
    Posts
    8

    Question Spark plug problems

    I have a 1974 Evinrude 9.9 outboard that the top cylinder spark plug keeps going bad. I was going to purchase 2 new coils but I think I might have got some bad spark plug. I have installed a new fuel pump and had carburator cleaned. Can anyone help me?

  2. #2
    Join Date
    Sep 2010
    Location
    ontario
    Posts
    9,033

    Default Re: Spark plug problems

    Sparkplugs really do not go bad.---------------There is a problem in the cylinder and not enuff heat is being produced.-------------So check and see if you have spark that will jump a gap of 3/8" or more on both cylinders.-----Is the thermostat in place and working properly ??. ----Have you checked compression ???------Have you checked the reed valves ??

  3. #3
    Join Date
    Oct 2011
    Location
    maplevalley WA
    Posts
    6,241

    Default Re: Spark plug problems

    If the compression is even did you try switching plugs. A spark gap test will tell you if the ignition needs to be addressed but it wouldnt hurt to check the point gap and see if the coils are not cracked. I normally have ignition parts on hand whenever pulling the flywheel. Plugs will foul if your rich on the oil mix are you running 50:1 the weaker burning plug will allways foul first. or the cylinder with the lowest compression.

  4. #4
    Join Date
    Feb 2012
    Location
    Madison, WV
    Posts
    8

    Default Re: Spark plug problems

    It has a new thermostat and working. I will check the spark and compression and get back to you in a day or two. Thanks

  5. #5
    Join Date
    Feb 2012
    Location
    Madison, WV
    Posts
    8

    Default Re: Spark plug problems

    I will check everything you addressed here. I can clean my fouled plug and no fire, install a new one and it will fire. Mixture may be a tad rich.

  6. #6
    Join Date
    Sep 2010
    Location
    ontario
    Posts
    9,033

    Default Re: Spark plug problems

    The cylinder has weak spark or there is not enough heat produced in the cylinder to keep the sparkplug clean !

  7. #7
    Join Date
    Oct 2011
    Location
    maplevalley WA
    Posts
    6,241

    Default Re: Spark plug problems

    I have allways had good luck with autolite plugs I believe they are the autolite 353s the champions seem to foul out easier.

  8. #8
    Join Date
    Oct 2011
    Location
    maplevalley WA
    Posts
    6,241

  9. #9
    Join Date
    Feb 2012
    Location
    Madison, WV
    Posts
    8

    Default Re: Spark plug problems

    Thanks guys. Will get back when I check everything out.

  10. #10
    Join Date
    Feb 2012
    Location
    Madison, WV
    Posts
    8

    Default Re: Spark plug problems

    OK guys, I checked the compression on both cylinders and got 115# on each one. Checked spark on plugs with an ark of 3/8" to 1/2". Checked points, not burnt and gapped right. The only thing I can find is plugs (wrong number) and the gas may be mixed wrong (a tad rich). I am going to get me a set of plugs and some new gas mixed and try it when the weather breaks. Will get back to you and let you know what happens. It only does this under load after I have ran it a while. 50:1 mixture.
    Last edited by Heathcliff48; 02-20-2012 at 03:19 PM.

  11. #11
    Join Date
    Feb 2012
    Location
    Madison, WV
    Posts
    8

    Default Re: Spark plug problems

    Can I start the engine after dark to check for spark on coils?

  12. #12
    Join Date
    Sep 2010
    Location
    ontario
    Posts
    9,033

    Default Re: Spark plug problems

    Sure why not.------Let us know if the warms up after it has run for a while.-------cylindehead should run at about 140 degrees F.

  13. #13
    Join Date
    Feb 2012
    Location
    Madison, WV
    Posts
    8

    Default Re: Spark plug problems

    Thanks, Racerone, will get back to you a little later. Allen

  14. #14
    Join Date
    Oct 2011
    Location
    maplevalley WA
    Posts
    6,241

    Default Re: Spark plug problems

    Give it the 6 second test after it warms up can you hold your hand on the head for six seconds. you want it hot but not too hot too touch. If it stays cool the t-stat is stuck open.

  15. #15
    Join Date
    Feb 2012
    Location
    Madison, WV
    Posts
    8

    Default Re: Spark plug problems

    Will do, kimc1, thanks.

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