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  1. #1
    Join Date
    Aug 2005
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    87

    Default 2-stroke won't run without choke

    Very simple Mariner5 air-cooled 2-stroke runs fine on half-choke , dies on anything less. I've had the carb off and cleaned it (though, oddly, I couldn't remove the main jet which is held up in place by a plug in the top of the float chamber . With plug removed the jet seems to levitate in the threaded hole , it rotates but neither rises nor falls)
    Gaskets seem fine .
    The idle jet screw does nothing, by the way. If the needle were worn you would think it would assist, if anything, in keeping the engine running.
    Something subtly wrong with the level of fuel in the float chamber? Float is not damaged (and it would have to float higher to starve the jet wouldn't it?)
    Sucking air through worn throttle spindle? Doesn't seem slack.Next session perhaps a drop of oil on the spindle while it's running might effect a very temporary cure , or at least be seen to be sucked in , and prove the point.
    Should I just adjust the choke control so that half-off is as far as it goes?
    What more can I do?

    Actually now that I see it in print I wonder if I have really cleaned the main jet if I've not removed it. It's had a soak with carb cleaner and a blow through that's all, though with a lamp shining through the carb I could see a pinpoint of light looking up-the-way through the jet.

  2. #2
    Join Date
    Jun 2001
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    5,935

    Default

    Quote Originally Posted by Mike2309 View Post
    Very simple Mariner5 air-cooled 2-stroke runs fine on half-choke , dies on anything less. I've had the carb off and cleaned it (though, oddly, I couldn't remove the main jet which is held up in place by a plug in the top of the float chamber . With plug removed the jet seems to levitate in the threaded hole , it rotates but neither rises nor falls)
    Gaskets seem fine .
    The idle jet screw does nothing, by the way. If the needle were worn you would think it would assist, if anything, in keeping the engine running.
    Something subtly wrong with the level of fuel in the float chamber? Float is not damaged (and it would have to float higher to starve the jet wouldn't it?)
    Sucking air through worn throttle spindle? Doesn't seem slack.Next session perhaps a drop of oil on the spindle while it's running might effect a very temporary cure , or at least be seen to be sucked in , and prove the point.
    Should I just adjust the choke control so that half-off is as far as it goes?
    What more can I do?

    Actually now that I see it in print I wonder if I have really cleaned the main jet if I've not removed it. It's had a soak with carb cleaner and a blow through that's all, though with a lamp shining through the carb I could see a pinpoint of light looking up-the-way through the jet.


    Do you push the carb up as far as it will go in the sleeve before clamping it up. If you dont then air will leak in at the clamp. It is possible there should be an O ring. I had the same problem with a similar Yanma.
    Eastern Scotland and beyond.

  3. #3
    Join Date
    Aug 2005
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    87

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    "Do you push the carb up as far as it will go in the sleeve before clamping it up. "

    Do you mean the jet there ? If so I'll check that. Thanks.

  4. #4
    VicS is offline Registered User
    Location : Home: Kent. Boat: Chichester
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    Jul 2002
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    Default

    Quote Originally Posted by Mike2309 View Post
    Very simple Mariner5 air-cooled 2-stroke runs fine on half-choke , dies on anything less. I've had the carb off and cleaned it (though, oddly, I couldn't remove the main jet which is held up in place by a plug in the top of the float chamber . With plug removed the jet seems to levitate in the threaded hole , it rotates but neither rises nor falls)
    Gaskets seem fine .
    The idle jet screw does nothing, by the way. If the needle were worn you would think it would assist, if anything, in keeping the engine running.
    Something subtly wrong with the level of fuel in the float chamber? Float is not damaged (and it would have to float higher to starve the jet wouldn't it?)
    Sucking air through worn throttle spindle? Doesn't seem slack.Next session perhaps a drop of oil on the spindle while it's running might effect a very temporary cure , or at least be seen to be sucked in , and prove the point.
    Should I just adjust the choke control so that half-off is as far as it goes?
    What more can I do?

    Actually now that I see it in print I wonder if I have really cleaned the main jet if I've not removed it. It's had a soak with carb cleaner and a blow through that's all, though with a lamp shining through the carb I could see a pinpoint of light looking up-the-way through the jet
    .
    What is the serial number of the engine. ?

    Running only when choked is usually a sign of a dirty carb

    Does the carb look like http://www.boats.net/images/diagrams.../822367/15.png
    If it does I would say remove and clean the main nozzle #6 by pushing a soft copper wire through it. It is not good enough to be able to see a pin point of light through it . Watch out for the gaskets #5 and #7.

    Clean also all the jets # 8, 10,11 and 12.

    The float should be adjusted so that the needle valve just closes when the float is horizontal / parallel with the float chamber to carb body joint
    Last edited by VicS; 19-06-12 at 23:07.
    Sea Wych Owners Association: www.Seawych.org

  5. #5
    SAMYL is offline Registered User
    Location : Strangford/Belfast
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    Make sure the main jet is clean, not just light shining through!
    If the main jet is gummed up then there is a fair chance the float needle will be gummed up too leading to a poor fuel supply.
    Throttle valve spindles need to be seriously worn to affect normal running so I would probably discount that.
    Have you checked that the air bleed screw in the tank filler cap is opening properly and have you cleaned the fuel filter at the fuel tap? The actual plastic fuel lines gum up as well and need cleaned out too on a regular basis. Check too the pipe where the fuel goes into the carb, i.e. between the fuel supply pipe and the float valve.
    If your carb is fitted with a fuel pump diaphram you may find it may be leaking and need replacing.

    In effect, clean EVERYTHING between the filler cap and the crankcase!!

    These engines can be a bit temperamental, mine will not even start without the choke even when hot. Best of luck.

  6. #6
    Join Date
    Aug 2005
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    87

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    Quote Originally Posted by VicS View Post
    What is the serial number of the engine. ?

    Running only when choked is usually a sign of a dirty carb

    Does the carb look like http://www.boats.net/images/diagrams.../822367/15.png
    If it does I would say remove and clean the main nozzle #6 by pushing a soft copper wire through it. It is not good enough to be able to see a pin point of light through it . Watch out for the gaskets #5 and #7.

    Clean also all the jets # 8, 10,11 and 12.

    The float should be adjusted so that the needle valve just closes when the float is horizontal / parallel with the float chamber to carb body joint
    Thanks for that. It's pretty much like that but there are no jets 10 and11 under the plate, and the float does not have integral pivot it bears (up)on a sort of pivotting wishbone . Adjusting the level would mean bending that wishbone I presume.

  7. #7
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    Aug 2005
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    Quote Originally Posted by SAMYL View Post
    Make sure the main jet is clean, not just light shining through!
    If the main jet is gummed up then there is a fair chance the float needle will be gummed up too leading to a poor fuel supply.
    Throttle valve spindles need to be seriously worn to affect normal running so I would probably discount that.
    Have you checked that the air bleed screw in the tank filler cap is opening properly and have you cleaned the fuel filter at the fuel tap? The actual plastic fuel lines gum up as well and need cleaned out too on a regular basis. Check too the pipe where the fuel goes into the carb, i.e. between the fuel supply pipe and the float valve.
    If your carb is fitted with a fuel pump diaphram you may find it may be leaking and need replacing.

    In effect, clean EVERYTHING between the filler cap and the crankcase!!

    These engines can be a bit temperamental, mine will not even start without the choke even when hot. Best of luck.
    I've replaced fuel lines and filter, and it has an external tank, so I've covered some of the above. I'll try the rest of it on some evening that England have not just beaten the Ukraine 1-0 to progress beyond the group stage of .........

  8. #8
    VicS is offline Registered User
    Location : Home: Kent. Boat: Chichester
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    Sounds like an old rebadged Yamaha one.

    Yes the float adjustment will be made by bending the yoke but it should not the overly critical. I dont know what the correct height is
    Last edited by VicS; 20-06-12 at 00:13.
    Sea Wych Owners Association: www.Seawych.org

  9. #9
    Join Date
    Aug 2005
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    thanks again Vic.
    Didn't give you the serial number before, it's 661 312426.The diag of the carb (although it's not exactly the same as mine) does explain why I couldn't get the main jet out. Mind you, how do you get it out against the grip of those two O rings? is it okay to push it down from above ?
    I've been in touch with Outboards Direct for availability of gaskets etc (recommended in this forum I think) but they have a health/medical situation at the moment and are unable to reply.

  10. #10
    VicS is offline Registered User
    Location : Home: Kent. Boat: Chichester
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    The diagram is the one for that number ...1979 model.

    Id think you will have to be very careful about pushing that nozzle out. Easily damaged Id think. I dont know if its possible to clean it properly in situ or not.

    If you cannot get any help from Oakley I guess you will have to take pot luck with the Dealer list on the Mariner website
    Sea Wych Owners Association: www.Seawych.org

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