Iginition circuit showing components types for a 20 Hp Yahama outboard

Discussion in 'OnBoard Electronics & Controls' started by BertKu, Dec 15, 2020.

  1. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    I was so lucky that somebody gave me a 20 Hp Yahama old style outboard motor as a present, but it does not have an ignition unit. I have to create and make one, but has no clue what to make.
    Some info:
    2 Cylinder
    Not electric starting, but by pulling a string
    The build in starting coil generates , approx 2 x 300 Volt per half turn
    The 2 bougie (sparkplugs) coils generates the sparkplug high voltage
    The system gives 2 x indications when I could charge a capacitor.
    Somehow I have to dump the charged capacitor into the 2 sparkplug coils.

    What should I use. 2 x Thyristors? 2x High Voltage capacitors ?
    Who has a circuit diagram for me or can lead me in the right direction.
    Bert.
     
  2. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    A tall order afaik.

    I would try to buy an aftermarket replacement.
     
  3. philSweet
    Joined: May 2008
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    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    Some basic info would be nice. How old, in what language are the casting alphanumerics written, and is there a model number?
     
  4. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    Hi PhilSweet, Thank you for responding. Unfortunately I have no idea how old the motor is. attach I have the photo of the serial number plate. I suspect that there is more problems than only the ignition box missing, therefore I like to make a simple circuit just to see whether the motor will kick in. Also I like to check whether the energizing coil is giving the right voltage off and whether the sparkplug coils are both in tact, before spending money on it. Also I like to check the impeller then I will do my best to purchase in this part of the world something what works better than I create. I build a number of electric motors by writing the software, making and welding the frame, making the pc boards and electronic, making it all work, but a 2 cylinder petrol (gas) engine is way outside my field of expertise. Photos attached of one my motor creation and serial number plate of the 2 Yamaha.
     

    Attached Files:

  5. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    Hi Philsweet, I may be mistaken and mislead. I think it is an 35 Hp engine from Evinrude. That is a big surprise. Why a Yamaha casing ??? Puzzles, and puzzles to solve.
    Bert
    upload_2020-12-16_12-17-41.png
     
  6. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    Thank you Fallguy, I will only try to do that if I have been able to make this engine running in principle. Bert
     
  7. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    I took the cover off and this is the view of the engine. In principle it should not be difficult to make a ignition unit. Please correct me where I am going wrong.
    The generating coil passes the magnet and it creates a pulse. This pulse I will feed into a high voltage capacitor. The coil turns slightly and it passes a trigger unit which is with speed moved closer or further away. This pulse I feed into a Flipflop which select in which sparkplug the charged capacitor is being discharged. The discharged capacitor is again recharged by 180 degrees movement of the coil and the capacitor gets charged again. passes the trigger and get now discharged into the next sparkplug circuit, selected by the trigger and flipflop. Simple , yes, but the Devil sits always in a tiny little corner by overlooking something. Where heave I gone wrong? . Bert

    P.S. the serial no is 358B63B which indicates that its is an Evinrude 1978 model !!
     

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    Last edited: Dec 16, 2020
  8. philSweet
    Joined: May 2008
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    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    Last edited: Dec 16, 2020
  9. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member



    Thank you so much, great info and it is what I thought, but still has to figure out an flipflop system as mine is manual flywheel started with a puller cord. A flipflop is easy, but if the engine stops, which sparkplug has to start first and that is where I will have to "hammer my brains on". But we will get it right. Thank you, for the lead and circuit diagram. Bert
     

  10. BertKu
    Joined: May 2009
    Posts: 2,498
    Likes: 43, Points: 58, Legacy Rep: 223
    Location: South Africa Little Brak River

    BertKu Senior Member

    Thanks for the link, No I am not so brave to tackle a Mercury complex system. I think this is the circuit diagram of the one I have been given. The black box as hereunder vvvvvvvvv I have to create. Will be fun. Bert
    [​IMG]
     
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