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  1. #1
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    Opti spark plugs are black

    I just finished year two with my 200XS ROS. Great motor. Year one, break in and maybe another hour, the plugs came out black. Year two, ran a few tanks of gas through it, plugs came out black when I pulled them to fog the motor.

    Is this normal?
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  2. #2
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    Hi David - let' start with the plug # just to be certain of the correct plug - my Parts Manual revised 2017 version shows an NGK 1ZFR7M . but I believe a discussion on here was that a supplement for gen 2 showed a 1zfr5g was correct - the 5 is supposed to be 2 ranges hotter . I can only confirm what my revised parts manual shows - 7m.
    On the Service Manual of February 2001 so it' gen 1 shows NGK -PZFR5F-11 . Heavy Duty - gapped at 40 So this is all the info I have available other than calling merc tech , but i suspect the call should be made to ascertain the correct info on the subject.
    I did not recieve a supplement with my ServiceManual . So there may be more to the story and the thread on here may be correct - but sometimes things get mixed up in translation and it got crossed up . Remember my pats manual is up to date but a supplement may still Trump that . Doubtful though since it' 2017 . Let' see if we can stir a Master Tech up for an answer-
    Last edited by kellytheaker; 10-25-2019 at 10:28 PM. Reason: Correcting

  3. #3
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    How many hours on engine? When I had a 300XS I had the injectors(fuel/air) cleaned at about 180hrs because plugs were way blacker than yours. Also had some buildup on top of pistons. But overall if it runs good be happy!
    http://www.stvowners.com

    Checkmate 2002 Convincor 270 496 MAG-HO

    2003 Cougar 22MTR w/300xs SOLD
    90 21Skater w/300xs - sold
    98 STV Euroski w/280 - sold


    2006 Trailblazer SS 6.0l 395hp

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  5. #4
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    David , had mine on a stand and pulled a plug for your reference and was 7M . Burn on #2 showed dark brown visual on open side and carbon dark on rest of plug surround . Rememer this would have been an idle , cool run into dock . This plug #2 was as expected - i thought anyway - when I fog I will have a more consistent finding for you to compare to . So anyonr have this supplement to the manual Stating different plug ?

  6. #5
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    Should get injectors serviced as well. I get mine done before every season and a few of the air injectors are caked with carbon build up

  7. #6
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    Maybe 20 hours on the engine

  8. #7
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    David - I went to fog the motor and only got 1 bank of plugs done and all looking similar , ceramic is a nice dark brown in phases it seems . White areas then back to a dkbrown in a pattern **** the darkest at back of elective opening . I will be certain of the other bank tomorrow - when I get another can to finish up . You didn' by chance introduce a break in again - delivering an oil rich delivery? Or I suspect you putted around a bunch before putting away last run since it' a tad chilly . You have not stated the plug but suspect 7m

  9. #8
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    When I had my 300xs, was told not to fog the engine because could foul the injectors. not sure if it's changed?
    http://www.stvowners.com

    Checkmate 2002 Convincor 270 496 MAG-HO

    2003 Cougar 22MTR w/300xs SOLD
    90 21Skater w/300xs - sold
    98 STV Euroski w/280 - sold


    2006 Trailblazer SS 6.0l 395hp

  10. #9
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    I thought it was a good thing for the bore and rings ,but now you got me thinking . Can anyone else confirm this statement . Thanks for bringing that forward .

  11. #10
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    Dark plugs are normal for an opti on 91. They only run 90-110psi compression for an average. Lots of soot and carbon from running water cooled fuel into 110 compression.
    Try to find a low rvp fuel as standard v-grade and a-grade is close to 10rvp look for 8 or less. Iíve been splashing vp4sse to cut rvp
    Ohm the plug from end to tip if only a small spot is 5000 ohm theyíre do for a clean or replacement.

    Honestly were here supposed to replace the crush rings each time you pull it out to see them.

    I find more broken in the nut then fouled. But a batch of weak 91 can black them um good

    Run some pea type cleaner to keep them clean.

    As for fogging i dont think it hurts. But merc doesnít recommend it. They squirt dfi in the spark hole and manualy rotate the engine to oil the rings and bore. I use a spray bottle myself just for a finer mist.
    Last edited by Motv18; 10-27-2019 at 09:46 PM.

  12. #11
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    My mechanic says don't worry. Idles well, runs hard at top end, relax

  13. #12
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    That is a normal plug for an Opti. Remember it is a 2 stroke. The tip is brown = good burn.

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