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  1. #1
    Join Date
    Oct 2017
    Location
    Dorothy NJ
    Posts
    4

    Default 1984 Johnson 140 V4 crapping out

    Hi and thx for reading this. My motor has always started a little rough but run pretty well after starting. Now after starting up and moving at trolling speed for about 5 minutes the motor craps out and won't start for a while. Last 3 test runs were identical but I may have tried to slow down or speed up when it actually died. I've heard it could overheating somehow, bad thermostat, bad coils, head gasket, etc.. I've worked on motors in the past but not sure how to diagnose this issue. Any help is greatly appreciated, hoping to fix this before striper season.

  2. #2
    Join Date
    Sep 2010
    Location
    ontario
    Posts
    13,669

    Default Re: 1984 Johnson 140 V4 crapping out

    You start with a compression test on those.------They have a history of breaking the piston rings.

  3. #3
    Join Date
    Oct 2017
    Location
    Dorothy NJ
    Posts
    4

    Default Re: 1984 Johnson 140 V4 crapping out

    Thanks racerone, I'm on it

  4. #4

    Default Re: 1984 Johnson 140 V4 crapping out

    Sounds like you may be fouling the plugs? May be running rich at low speed?

  5. #5
    Join Date
    Oct 2017
    Location
    Dorothy NJ
    Posts
    4

    Default Re: 1984 Johnson 140 V4 crapping out

    Thx Blueghost. The plugs are new, I change them and clean connections every year because they have been an issue in the past. I have also had problems with acceleration before and I believe my mechanic replaced a head gasket to fix it. It's hard for me to figure out because it runs fine on the trailer with the muffs but dies 5 minutes away from the dock and will not restart for about a half hour. Cooling system seems ok as well

  6. #6

    Default Re: 1984 Johnson 140 V4 crapping out

    That sounds like a faulty pick up coil… I've seen that many times was snowmobile engines ...Work great when they're cold and then they die when they eat up Does it die suddenly or slowly falter ?

  7. #7
    Join Date
    Sep 2010
    Location
    ontario
    Posts
    13,669

    Default Re: 1984 Johnson 140 V4 crapping out

    Testing is what you do.----Put a timing light on it and see what happens to spark as you pull away from the dock.

  8. #8

    Default Re: 1984 Johnson 140 V4 crapping out

    Have you check for spark when it quits? I doubt it's a fuel related issue… Maybe cooling

  9. #9
    Join Date
    Oct 2017
    Location
    Dorothy NJ
    Posts
    4

    Default Re: 1984 Johnson 140 V4 crapping out

    I'm ordering the new coils now, pretty cheap so why not replace them. I'll check the timing once I get them put on and let you know how it goes. Thx again guys!

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