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  1. #1
    Member
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    Jan 2018
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    Normal??? Black buildup in prop hub

    05 Opti 200... 1b176241

    Ok, so lately I’ve been able to get out more and the motor has been running and sounding great. History and previous work is viewable in previous posts. I run the “cocktail” with every fill up of 89oct w/ no more than 10% eth. (seems to be all I find when I stop to fill up).

    Question: how long, if ever, will I stop getting so much black exhaust deposit on the inside of the prop barrel? It’s not just a light coating now but after 40 gal or so it’s built up and lightly tacky. If there could be an underlying issue please let me know.

    Thanks in advance.



  2. Member
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    Mar 2017
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    Tuscumbia, AL
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    #2
    Somewhat normal. It will be much less if you run the correct 87 octane gas and make a good 5000+ rpm run back to the ramp before you put it on the trailer.

  3. Member
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    Jul 2004
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    Penn PA
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    #3
    Run it wide open all the time and it will be clean.



  4. Member
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    Feb 2010
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    Mooresburg, TN/Lake Placid, FL
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    #4
    I would suggest using 87 octane as this is what the motor calls for. If I recall, the 89 and 93 burn cooler and cause more carbon build-up. Since you are using the cocktail, longer hish spped runs will help clear the carbon...


    George Brock

    2015 920 Pro/XP
    2015 Mercury 250 Pro/XS
    Twin 8' Powerpole Blades

  5. Member
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    Jan 2018
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    Kentucky
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    #5
    87 it is. I’ll watch it and see if it decreases. Thanks guys

  6. Scraps
    Join Date
    Apr 2007
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    Havertown, PA
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    9,586
    #6
    I know I thought I was being smarter with my first year burning some 89 octance. Not necessary and I noticed my plugs had more carbon buildup due to the cooler burning higher octane.
    2017 Phoenix 819
    2016 200ProXS, s/n 2B359849, Mod 1200P73BD

  7. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    Apr 2008
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    Greenville, SC (US)
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    94,941
    #7
    It does make a difference!

    Avoid excessive idling- the engine runs it's "dirtiest" at IDLE and WOT.

    Cleanest operation happens to be right where it gets it's best fuel economy (3500-5000 RPM range). Good range for a nice run at the end of each outing.


    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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