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  1. #61

    Default Re: 76 jhonson 15hp no spark

    I didn't want to start a new thread so just figured id keep this going. The 1974 I bought runs great now that I cleaned the carb and rebuilt the fuel pump. but I notoced when I choke it gas runs out of the butterfly. Is this normal when its running is it just flooding itself out.

  2. #62
    Join Date
    Feb 2001
    Location
    Central West Florida
    Posts
    15,692

    Default Re: 76 jhonson 15hp no spark

    If, when you choke it the engine doesn't start... that fuel has to spill over somewhere.
    We occasionally have questions. If you fail to answer, it may affect ours.

  3. #63

    Default Re: 76 jhonson 15hp no spark

    Quote Originally Posted by joereeves View Post
    If, when you choke it the engine doesn't start... that fuel has to spill over somewhere.
    I figured as much just wanted to be sure. I found a post of yours on setting the carb follwed it to a T and it starts and runs perfectly. im glad I found this website it has helped tremendously.

  4. #64

    Default Re: 76 jhonson 15hp no spark

    I got the carb rebuilt and its leaking fuel all around the bowl gasket. im not sure why it would be leaking fuel there

  5. #65
    Join Date
    Feb 2001
    Location
    Central West Florida
    Posts
    15,692

    Default Re: 76 jhonson 15hp no spark

    If a plastic float chamber, it could be warped. If so, dress it up with #400 wet/dry black sandpaper... the sandpaper wet down with mineral spirits.

    Could be a float set wrong. If so, correct as follows.
    ********************
    (Carburetor Float Setting)
    (J. Reeves)

    With the carburetor body held upside down, the float being viewed from the side, adjust the float so that the free end of the float (the end opposite the hinge pin) is ever so slightly higher (just ever so slightly off level) than the other end. And when viewed from the end, make sure it is not cocked.

    ********************
    We occasionally have questions. If you fail to answer, it may affect ours.

  6. #66

    Default Re: 76 jhonson 15hp no spark

    success no more fuel leaks changed the float and readjusted it. thanks again

  7. #67
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    2,005

    Default Re: 76 jhonson 15hp no spark

    Now don't forget the compression report on the other 15 to see if it goes up or down as you lake test it.

  8. #68

    Default Re: 76 jhonson 15hp no spark

    I finally got to lake test the 15 that went swimming. it definitely seemed underpowered. but it was a heavy old fiberglass boat and about 400lbs of ppl on the boat. That may have been the reason but it starts so easy and runs awsome. im going to compression test this week since ive got to run it a little.

  9. #69
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    2,005

    Default Re: 76 jhonson 15hp no spark

    Okay, sounds like a heavy load for a 15.

  10. #70

    Default Re: 76 jhonson 15hp no spark

    When you are concerned about under power it is a good idea to do a cylinder drop test to confirm both cylinders are firing. With insulated pliers, pull one spark plug boot at a time. If the motor stalls, then you know the other cylinder was not firing or is very weak. Those motors can run remarkably well on only one cylinder but with significantly reduced power at the top end. At idle you would never know only one cylinder was working, without the drop test.

    I suspect your low compression cylinder was never firing and hence why you noticed the reduced power. It was a heavy load you were pushing but those 15Hp put out a lot of punch, when opened up, so a cylinder drop test might shed some light on the issue.

  11. #71

    Default Re: 76 jhonson 15hp no spark

    I will try the test but both cylinders were firing fine. I took the motor out again yesterday and with 2 guys in a light aluminum boat it did fine.

  12. #72

    Default Re: 76 jhonson 15hp no spark

    I did another compression test today after running the motor twice on the lake. now both cylinders are between 90 and 95 psi. im happy with it for now

  13. #73
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    2,005

    Default Re: 76 jhonson 15hp no spark

    That is not bad compression for what its been through. After a few more gallons of fuel, check compression again. If it is exactly the same, then it may live out a decent life.

  14. #74

    Default Re: 76 jhonson 15hp no spark

    ive been renting a tester from oriellys thinking about just buying one. is there a brand you would recommend. I was happy to see both cylinders were the same readings.

  15. #75
    Join Date
    Mar 2019
    Location
    Southern Ontario, Canada
    Posts
    14

    Default Re: 76 jhonson 15hp no spark

    Quote Originally Posted by outback32 View Post
    ive been renting a tester from oriellys thinking about just buying one. is there a brand you would recommend. I was happy to see both cylinders were the same readings.
    I'm happy with my Lisle 20250 tester.

  16. #76
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    2,005

    Default Re: 76 jhonson 15hp no spark

    Thanks for the answer, Johnny. Lisle is a pretty good product.

  17. #77

    Default Re: 76 jhonson 15hp no spark

    I just had a no spark issue on my 9.9 and it turned out to be a broken core inside of a spark plug even though it made spark to the block it didn't make Spark across the electrode Gap

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