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  1. #1
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    2.6 Carb idle issues

    Hi Guru's

    I have an old 150HP powerhead that I have just fired up again after 4 years of sitting around.
    Its amazing once I got everything installed again it fired right up.

    However the thing didn't sound right at idle like it had a bad miss.

    I have worked through a number of things but before I get started the entire ignition system was running nicely on another motor.

    Long story short I have used coils that were working fine, on the previous engine and even moved them between cylinders as 5 and 6 work fine with all of the coils.
    Now I have swapped out every other part from that motor trying to resolve this issue.

    Powerpack
    CDI unit
    Stator
    and pulser coils
    count less plug changes

    Nothing has made a difference.

    I have not disassembled the carbs but have used an airline on the following:

    Main jets
    idle jets
    air bleed
    idle mixture port etc...

    Have also carried a compression test which was fine.

    No matter what I do if I remove a plug wire on 1, 2,3 or 4 cylinders at idle not much changes, if I remove the wires on cylinders 5 and 6 big change.

    All the plugs are wet so I assume fuel is not an issue.

    My question is, is there some odd idle mode in these things that at idle where cylinders 5 and 6 do most of the work and 1 - 4 fire randomly? Then over a certain RPM they all fire properly?
    Its not the end of the world as I ran it up to sell it and have proved the rotating assembly is fine so the new owner is happy its just bugging me.

    Cheers
    Last edited by 225XCL; 01-25-2018 at 12:20 AM.


    Sold the old Formula 233.
    Now have a 22ft Whittley Sea Legend powered by 225 Excel with Pro-V 200 covers.

  2. #2
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    Check your fuel pumps, bet a pressure diaphragm is blown. That would make 2-4-6 run somewhat richer. A quick check is to leave the hoses on, remove the fuel pumps (both), turn them so you can see the pressure port (center hole). Have someone squeeze the fuel primer bulb and see if fuel comes out of the pressure port. If so replace both fuel pumps and you should be good to go.

  3. #3
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    Thanks very much. Would make sense as its the only think I hadn't swapped out from the other engine.

    I did change one of them but it was one I had lying around and could also be garbage.


    Sold the old Formula 233.
    Now have a 22ft Whittley Sea Legend powered by 225 Excel with Pro-V 200 covers.

  4. #4
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    You see any fuel come out of the carbs? I would go there next if the fuel pumps are good. Let us know what you find.

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  6. #5
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    Parry Sound, On
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    If it's me, I'd check and clean the pilot jets. Pull the bowls and the little brass screws on the bottom. Then soak, blow and use a torch tip cleaner to run through them. They are pretty small compared to every other jet on that motor so it doesn't take much to mess with them.

    If you have a fuel bulb you can test your fuel pumps and needles by pumping it up hard then keep your hand on it and slow squeeze. If you can feel a pressure drop you've got something leaking. Pumps don't age well so it's not a bad idea to start there.
    '08 SRV
    Yamaha 3.1 Phase III


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  8. #6
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    Make sure that the carbs are horizontal.

    90 degree V6 Yamahas don't idle very well when trimmed out.
    Markus' Performance Boating Links:
    www.toastedmarshmallow.com/performance

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  10. #7
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    Hi Dok, I did give them a blast with the airline but as you say they are very small and may have required further attention.

    I have passed all the help information over to the new owner along with an extra set of carbs, plus he has his old carbs and pumps that can be swapped over.

    Cheers
    Jason


    Sold the old Formula 233.
    Now have a 22ft Whittley Sea Legend powered by 225 Excel with Pro-V 200 covers.

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