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  1. #1
    Join Date
    Mar 2007
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    winder, georgia, united states
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    21

    Default 1978 mercury 115 inline six carburetor trouble

    I've been toying around with this motor for a while now with no experience and I've almost got it where I want it. My issue now is the carburetor. At first it wasn't getting gas so I took it apart and cleaned it. Then gas was pouring out I replaced the one needle. So now after tinkering with it the top carb leaks and the bottom two I can't even tell if they are getting gas. The motor runs so I'm guessing their getting gas or it would shut off right? The flat head on the bottom is old and I can't get it loose to clean. When I pump the bulb it does not get hard you just see gas start dripping from the carb. What does it sound like I need to do?

  2. #2
    Join Date
    Sep 2010
    Location
    ontario
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    13,802

    Default Re: 1978 mercury 115 inline six carburetor trouble

    Oil goes into the engine via the carburetors.-----It is important to correct any problems.----Visit ---utube----for tutorial on carburetor work.

  3. #3
    Join Date
    Mar 2007
    Location
    winder, georgia, united states
    Posts
    21

    Default Re: 1978 mercury 115 inline six carburetor trouble

    Today I tried pulling plug wires while it was running and there was a difference in how it ran on each plug. The top carb still leaks by. I tried bending the tab a little and it seemed to work at first but it's dripping out of the top carb. When looking inside the throat I can see gas in the top man jet but I cannot see gas in the lower two. I also put in new plugs and each old plug had oil on it. Should I just invest in rebuilding all carbs or is there something simple I'm missing here?

  4. #4
    Join Date
    Sep 2010
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    ontario
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    13,802

    Default Re: 1978 mercury 115 inline six carburetor trouble

    Your decision.-----All I can say is that it is important to have clean / properly working carburetors.----Or you risk major damage to your motor.

  5. #5
    Join Date
    Mar 2007
    Location
    winder, georgia, united states
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    Default Re: 1978 mercury 115 inline six carburetor trouble

    So does gas supposed to be coming out of main jet tube
    while idling?

  6. #6
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    15,263

    Default Re: 1978 mercury 115 inline six carburetor trouble

    No. The float level is either too high, or the needle and seat are not working properly.

    Jeff

  7. #7
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    2,616

    Default Re: 1978 mercury 115 inline six carburetor trouble

    If its the foam float it could be heavy from ethanol damage....
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  8. #8
    Join Date
    Mar 2007
    Location
    winder, georgia, united states
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    Default Re: 1978 mercury 115 inline six carburetor trouble

    Quote Originally Posted by faztbullet View Post
    If its the foam float it could be heavy from ethanol damage....
    It's the black plastic float. It just has a small spring on top.

  9. #9
    Join Date
    Nov 2011
    Location
    tennessee
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    2,616

    Default Re: 1978 mercury 115 inline six carburetor trouble

    The plastic floats are off white...the black one is a foam float.
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  10. #10
    Join Date
    Mar 2007
    Location
    winder, georgia, united states
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    Default Re: 1978 mercury 115 inline six carburetor trouble

    I fixed the carb problem. It turns out the levers that the float uses to push the needle up is pretty touchy. The manual said to have a quarter inch of space between the bottom lever and the top while it is relaxed. Now there is a rattling noise coming from the flywheel. There was a little oil spitting from the bottom of the engine and I found a small tube that runs from the top of the engine to the bottom that was unhooked. Is this how oil is introduced to the top of the engine?

  11. #11
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    2,616

    Default Re: 1978 mercury 115 inline six carburetor trouble

    That what oils the top crank bearing.....
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  12. #12
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
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    Default Re: 1978 mercury 115 inline six carburetor trouble

    Check the tightness of the 8 bolts holding the flywheel to the hub. Then make sure there's a flat washer under the nut, one that nearly fills the opening. I had one with a washer that was too small in outer diameter and it rattled like crazy.

    Jeff

  13. #13
    Join Date
    Sep 2010
    Location
    ontario
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    Default Re: 1978 mercury 115 inline six carburetor trouble

    Sounds like the flexplate on the flywheel might be cracked.----Check bleed restrictors behind bypss covers,------Likely 3 of the 5 are gone.-------I install 8-32 stainless setscrews with wee hole in place of the plastic junk.

  14. #14
    Join Date
    Mar 2007
    Location
    winder, georgia, united states
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    21

    Default Re: 1978 mercury 115 inline six carburetor trouble

    Quote Originally Posted by fastjeff View Post
    Check the tightness of the 8 bolts holding the flywheel to the hub. Then make sure there's a flat washer under the nut, one that nearly fills the opening. I had one with a washer that was too small in outer diameter and it rattled like crazy.

    Jeff
    Yeah I don't even think it has one. I guesse I need to remove it any way to get a better look at what's going on.

  15. #15
    Join Date
    Mar 2007
    Location
    winder, georgia, united states
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    Default Re: 1978 mercury 115 inline six carburetor trouble

    Yeah I'm hoping I didn't run it too long without oil. I didn't notice It was unhooked for a while.

  16. #16
    Join Date
    Mar 2007
    Location
    winder, georgia, united states
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    Default Re: 1978 mercury 115 inline six carburetor trouble

    Thank you guys for your comments. It's helping me out alot here. I really appreciate it.

  17. #17
    Join Date
    Mar 2007
    Location
    winder, georgia, united states
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    Default Re: 1978 mercury 115 inline six carburetor trouble

    Quote Originally Posted by fastjeff View Post
    Check the tightness of the 8 bolts holding the flywheel to the hub. Then make sure there's a flat washer under the nut, one that nearly fills the opening. I had one with a washer that was too small in outer diameter and it rattled like crazy.

    Jeff
    You were right! It was missing the washer. I replaced it and she runs like a sewing machine now. Thanks!

  18. #18
    Join Date
    Sep 2003
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    New Tripoli, PA, USA!
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    Default Re: 1978 mercury 115 inline six carburetor trouble

    Hot damn!

    Jeff

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