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  1. 11-09-2022, 01:36 AM #1
    Ganastas
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    Carburettor cleaning for 2011 Mercury outboard 75hp 2 stroke ELPTO

    Engine seems to be idling rough after first outing for season. I have owned from new but never cleaned carbs. Always use Quikleen and Quickare and never ethanol fuel. Decided to have go at removing and cleaning carburettors. Assume that other than possible idle mixture adjustments there are no other adjustments to do after reassembly? Just cleaning, installing new gaskets and reassemble as original?
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  2. EuropeanAM
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    #2 11-09-2022, 01:05 PM
    Actually, you must perform a complete Sync and Link procedure (very critical). See the "Engine Synchronization and Adjustments" section of the Mercury Service Manual.

    This is required any time the carbs are loosened or removed.


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  3. Ganastas
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    #3 11-09-2022, 02:40 PM
    Assume you are referring to carburettor synchronisation section only and not looking to do timing adjustments? I am unclear as to extent of what needs to be done. Can you advise please?
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  4. EuropeanAM
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    #4 11-09-2022, 04:31 PM
    Technically ALL of them should be done, timing included.


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  5. Ganastas
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    #5 11-10-2022, 01:41 AM
    Are there any relatively straight forward electrical test I can do first to rule out electrical issue rather than just a suspicion that carbs need a clean? I started with compression check which delivered 132psi 125psi and 132psi then changed out plugs with an older set (not worn) which made not difference to rough idle. BTW the idle speed is 100rpm lower than normal and of course rough.
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  6. EuropeanAM
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    #6 11-10-2022, 07:14 PM
    Clip a timing light to each plug wire, one at a time, while the engine is running. Monitor the light for a steady flashing pattern.

    No pattern: No spark on that cylinder, OR a plug wire, OR a spark plug problem.


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  7. Ganastas
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    #7 11-12-2022, 06:54 PM
    Checked for spark and all good. Rebuilt carburettors and did link and sync. After running at idle for about 5min I noticed bottom carb as per attached photo
    IMG_5416.jpg
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  8. EuropeanAM
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    #8 11-16-2022, 01:19 PM
    Had it been trimmed up, or was it at level trim the entire time?

    If it had been level, are you running a portable fuel tank or built-in tank?

    Float checked for any type of mark or "divot" where the needle contacts the float tang?


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  9. Ganastas
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    #9 11-16-2022, 02:31 PM
    Pulled carbs off and noticed cable tie head stuck in one of reeds. Must have got sucked in. Looks like that was problem all along!

    IMG_5431.JPG
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  10. Ganastas
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    #10 11-16-2022, 02:35 PM
    BTW with regards to idle timing manual says to set to 5 degrees BTDC but also states a range of 2 degrees ATDC - 6 degrees BTDC. Why is that?
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  11. EuropeanAM
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    #11 11-16-2022, 02:46 PM
    Idle timing is used to set the idle speed... so it will vary within that range.

    Good catch on the tie wrap... anything left "loose" inside the cowling WILL end up in the engine (eventually).


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  12. greauxpete
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    #12 12-15-2022, 05:27 PM
    Good catch! I did the same thing you were doing on my 90 hp about 2 months ago. While your in there inspect the " ball check" in the manifold.

    See my thread here:

    https://www.bbcboards.net/showthread.php?t=1197362
    Last edited by greauxpete; 12-15-2022 at 05:35 PM.
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