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Thread: 1956 johnson 30

  1. #1
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    Default 1956 johnson 30

    Hey guys. I just found this site.
    I was wondering if someone could help me. I have just bought a 1956 Johnson 30. It's electric start. I don't have time to hook up the harness and cables to the boat this year, so I put a tiller handle on it. The handle came with a mercury tip swicth. I don't know where the wire should go. Also I bought the vacuum cut out swicth for it and mounted it. I hooked the vacuum hose to it, which was just hanging there, but I also don't know what wire should hook up to it. Any help would be great.

  2. #2
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    Default Re: 1956 johnson 30

    Super, the wire from the mercury switch connects to the housing of the vacuum safety switch. The center terminal of the vacuum safety switch is wired to the positive side of the breaker points for the lower cylinder.

  3. #3
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    Default Re: 1956 johnson 30

    Why does the mercury switch go to the housing? Doesn't the switch ground something and the vacuum switch is already grounded to the engine.

  4. #4
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    Default Re: 1956 johnson 30

    I'll stick my neck out here. Is that vacuum switch held by one bolt onto the bracket that supports the rewind starter and air silencer? I know the previous year was.

    If that is the case, the mercury switch is wired to the start button and completes the ground from the start push button. It allows starting only when the switch is tilted toward slow throttle settings.

    The next year, on the 35hp, the mercury switch did indeed go to the vacuum switch case, which was insulated from ground by a plastic mounting plate. It then served a dual function. Prevented starting at high throttle and also prevented the vacuum switch from operating at mid to high throttle settings.

    I'm just not sure which of these situations applies to the '56 30hp.

  5. #5
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    Default Re: 1956 johnson 30

    This time last year I had an RJE-18 scattered all over the garage. Now I'm up to my eyeballs with an RJE-19 scattered all over the garage. I was in the wrong gear when I posted. Frank is exactly correct. The mercury switch goes to the start button. The vacuum switch case is gounded via it's mount. The bottom cylinder points connect to the center post of it. I had to go out and look at mine to refresh myself. The '57 is a bit different than this. Good call, Frank, thanks for the correction.

  6. #6
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    Default Re: 1956 johnson 30

    Thanks for the replies. The mercury switch for starting makes sense to me. I just wonderind what the vacuum switch is for and by the way it is attached by one bolt to the recoil bracket. And what does attaching it to the the points do?

  7. #7
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    Default Re: 1956 johnson 30

    From the Johnson service manual:

    "Conditions under which the cut-out functions to limit maximum idling speed are as follows: If when running at fast idle in neutral (2000 RPM or more), the throttle is suddenly closed, a surge or sudden increase in manifold suction is introduced. Under influence of abnormal manifold suction in this instance, the fuel vapor mixture is not consistently ignited but will tend towards firing erratically (as combustible mixtures form*) to result in irregular but excessively “strong” power impulses to sharply increase motor RPM’s even though the throttle is closed – Resultant high motor speed (RPM’s) cannot under the circumstances be otherwise reduced or controlled by simply closing the throttle and since no manually operated ground switch is employed, other means are required – thus, the automatic cut-out..."

  8. #8
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    Default Re: 1956 johnson 30

    That was Engineer Talk for "If you rev it up with no load on it as in neutral or a broken shear pin, it won't slow back down". The vacuum cut-out switch cuts out one cylinder till it slows down.

  9. #9
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    Default Re: 1956 johnson 30

    Thanks. That makes perfect sense. I just wanted the make sure that I didn't need it to shut the motor off when I turn the tiller handle to stop. My 1957 7.5hp evinrude doesn't have one and it dies when I turn it to stop. Then someone told me that this 56 johnson would, it would stay running and that I would have to kill it another way. So you all have been great help. Thanks

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    Default Re: 1956 johnson 30

    That '56 didn't have a "kill" wire like more modern outboards. Nor did it have a wire coming from each set of points that killed the motor when shorted together, like later model big twins. I don't know about tiller models, but remote '56 and '57 models were stopped, by using the choke. At some point ('58, '59, '60, etc??) they provided the 2 wires from the points for shorting/killing.

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