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  1. #1
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    carbon build up / fouling plug(s) 150 opti

    serial 1B044209....

    long story short... friends were messing around on my boat a month or so ago having some drinks in the garage. motor got sent into break in mode.

    Did the maiden season voyage this past weekend, these plugs don't have too much idle time on them 10 mins on muffs. then warm up times on water I always usually run around 3000+ rpm through out the day (no extended putting around) until I got to boat launch then I putted around for about 10 mins waiting for trailer to load boat up.

    plug 5 has some major carbon built up on the ground strap from the exterior of the ground strap (near threads) to about half way up back of the strap, i've seen fouled plugs but to the point it had hard carbon build up on the back strap seems a little different to me? especially for plugs with at the most 10 hours on them. I got the boat late in the season last year and changed the plugs when i got it then...

    1st part of the day I did manage to hit close to 5400rpm if I can recall (it hit 55MPH on the nose GPS that i know for sure) then at some point it went down to 5100 and would crawl to maybe 5150 rpm at best and only pull 50ish mph)

    Motor has new belt, CCM reeds (blocks were lapped) new t stats last season. warm up temps hovered 150-149. running temps above 3000k rpm floated around 88F

    Plugs are IZFR5G gaped to spec.

    when i winterized the boat I did follow dons recommendations and did drop a touch of oil down each plug hole and fuel cocktail....

    Now what raises the concern for me is the hard carbon build up on the ground strap and that the PREVIOUS years plugs 1 of the plugs had the same style of build up.

    or is carbon build up in that sense somewhat common esp when a motor is back in break in mode? im assuming the variance in the plug darkness could vary as they all could of gotten a little bit more or less oil down the cyl when i winterized it... I know the previous plugs I changed out where all a consistent blackish color except the 5 and 6 being the worse ones.

    Cyl 1 -

    Cyl 2 -

    Cyl 3 -

    Cyl 4 -

    Cyl 5 -

    Cyl 6 -
    Last edited by ride.race.live; 06-11-2019 at 08:29 AM.
    2004 Ranger Reata 180vs 8" rapid jack magnum CCM reeds 21P tempest plus- 2005 150 optimax 1B044209

  2. Member
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    #2
    so ive been reading when the motor is in break in mode idling and going to wot can cause plug 5-6 to flood out.... would the correct way to deal with this until the "break in mode" is done is to just gradually accelerate ?

    New plugs on order but would like to make these last the break in period....
    2004 Ranger Reata 180vs 8" rapid jack magnum CCM reeds 21P tempest plus- 2005 150 optimax 1B044209

  3. Member lpugh's Avatar
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    #3
    try to spend a lot of driving time at about 4800, especially just before you come in, avoid idling and low rpm operation
    87 octane fuel only and quickleen
    Thank You Leon Pugh

  4. Member
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    #4
    yea my next time out ill plan on doing that. just want to more so verify the plugs I pulled isnt out of the norm for a motor in break in mode and that if I should "attack" it differently... so i dont foul out another bunch of plugs
    2004 Ranger Reata 180vs 8" rapid jack magnum CCM reeds 21P tempest plus- 2005 150 optimax 1B044209

  5. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #5
    Definitely too much idling, and the break-in mode is not helping at all.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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  6. Banned
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    #6
    All that slow running has fouled/carbon tracked a plug. Since the power was down when you opened it up, you may as well change plugs.

  7. Member
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    #7
    Damn tough not to idle that much lol. Felt like I didnt anyways....

    So I just bought a inline spark tester as it was 10bucks vs the timing light being 65....

    When I use the spark tester... can i unplug the plug wire and connect the tester on each cylinder as motor is running or will that cause issues
    2004 Ranger Reata 180vs 8" rapid jack magnum CCM reeds 21P tempest plus- 2005 150 optimax 1B044209

  8. Member lpugh's Avatar
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    #8
    I would recomend you shut it off to change cylinders or disconect the coil primary before dissconecting the plug while running. When you open circuit the secondary this forces the coil to produce its maximum voltage upward of 30 thousand volts, That voltage will go somewhere, thru you, arch to ground or collapse back into the primary side with a 500 plus voltage spike, most of the time no harm is done. Sometimes though rarely it will damage primary ignition componets
    Thank You Leon Pugh

  9. Banned
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    #9
    Quote Originally Posted by ride.race.live View Post
    Damn tough not to idle that much lol. Felt like I didnt anyways....

    So I just bought a inline spark tester as it was 10bucks vs the timing light being 65....

    When I use the spark tester... can i unplug the plug wire and connect the tester on each cylinder as motor is running or will that cause issues
    That won't tell you anything. You don't lose voltage at the wire if you have a bad plug.
    Change the plugs and run it hard to clean it out.

  10. Member
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    #10
    Yeah im changing both cyl 5 and 6 plug I wanted to use the tester to see if im maybe getting an issue before the spark plug.


    Ideally im hoping I can run the plugs (changing plug 5 and 6 though) until break in mode is done with.. once thats done with then i'd swap in all new plugs. or atleast thats my plan.

    I def need to get this break in mode over with by next month as I have a camping trip and supposed to bring people tubing / skiing... i know for a fact ill be idling a lot more then and definitely cant have the motor still in that break in mode.

    any one interested in a 150 opti and adding to my go fund me for a 150 4 stroke merc ? LOL (im dreaming)
    2004 Ranger Reata 180vs 8" rapid jack magnum CCM reeds 21P tempest plus- 2005 150 optimax 1B044209

  11. Member lpugh's Avatar
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    #11
    Replace all of those plugs, 1,2,4,5, and 6 are misfiring for sure under load and 3 may be.
    A timing light is good for a quick check for spark but can not tell you it there is enough available voltage to get the job done
    The gap type spark testers are fair for checking coil available voltage, so yes they do tell you much more than a timing light as they will force the coil to build near maximum voltage. If you found 5 coils would bridge a 1/2 in gap and one would only bridge a 1/4 gap, you have found a bad coil or a wire arching to ground or open ckt, Yes a open circuit wire can still pass current, just depends on the length of the open in the conductor
    Available voltage from the coils will depend on coil design, early systems jumping a 3/8 gap could be considered good, these systems would generally use plug gaps around .032. Later coils that use .040 or larger gaps should bridge a 1/2 in gap. The key for quick diag is they should all be about the same
    Last edited by lpugh; 06-13-2019 at 11:07 PM.
    Thank You Leon Pugh