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  1. #1

    Default Cutoff Switch/no spark Problem 33 HP Johnson

    1966 33 HP Johnson: I have no spark in the bottom cylinder and have traced it to the cutoff switch. If I remove and tape off the black lead coming from under the flywheel to the centre post of the switch I get a strong spark, I start the motor and it runs great - but of course it won't shut down using the key switch. I have checked for cracked wiring under the flywheel and tried a cutoff switch from another motor - no luck. Could this be a vacuum not wiring problem? can I ground the lead elsewhere so that the key switch works? Can I bypass this switch completely and maybe install a cutoff toggle near the key? I am really stumped.

  2. #2
    Supreme Mariner Joe Reeves's Avatar
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    Default Re: Cutoff Switch/no spark Problem 33 HP Johnson

    The wire that leads from under the flywheel connects to another wire at the center point of that cutoff switch. That other wire leads either to a push buttom stop switch or a ignition switch. I stropngly suspect that this second wire is either shorted out somewhere or is connected to a grounding component..... trace it out.
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  3. #3
    Commander lindy46's Avatar
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    Default Re: Cutoff Switch/no spark Problem 33 HP Johnson

    Cut-off switch has a vacuum line connected to the engine. Under high vacuum (runaway) the switch engages, and grounds out the cylinder. If the switch is broken, and always engaged, that cylinder will not fire. You can check the switch with an ohmmeter to the side post and center post. You should normally have no continuity. Suck on the vacuum hose and you should have continuity. Of course, you can bypass the switch by connecting the wire from under the flywheel directly to the wire going to the ignition switch, but I wouldn't recommend that, as the motor can't be killed during a runaway.

  4. #4

    Red face Re: Cutoff Switch/no spark Problem 33 HP Johnson

    Quote Originally Posted by Joe Reeves View Post
    The wire that leads from under the flywheel connects to another wire at the center point of that cutoff switch. That other wire leads either to a push buttom stop switch or a ignition switch. I stropngly suspect that this second wire is either shorted out somewhere or is connected to a grounding component..... trace it out.

    Thanks a million for this. Sometimes I stare at a problem too long and don't see the obvious. I had grounded the radio to an M terminal in the starter switch. Redid the switch today and took a common ground from the battery to the front of the boat for the accessories.

    Just fired her up and sparks all around.

  5. #5
    Supreme Mariner Joe Reeves's Avatar
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    Default Re: Cutoff Switch/no spark Problem 33 HP Johnson

    Quote Originally Posted by sapper29 View Post
    I had grounded the radio to an M terminal in the starter switch.
    DO NOT ever ground anything to the "M" terminals...... Why? Well. I'm glad you asked........

    Any component or accessory that has voltage (normally 12 volts) applied to it has that voltage running thru the component/accessory and finally out of that component/accessory thru (usually) a black wire to the negative side of the battery either directly or indirectly. This means that the ground wire of that component/accessory contains voltage. The result is (if connected to either "M" terminal) that voltage is now being applied to the points, condenser, and the coil..... really not a good idea!
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