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Thread: carb problem

  1. #1

    Default carb problem

    1982 mercury 80 hp , Motor starts great won't idle below 1000-1100 rpm , top carb adjusted 1 1/2 turns out, bottom carb adjusted all the way in to run best . What causes this ? I am New here

  2. #2
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    3,847

    Default Re: carb problem

    Do a compression test and open air spark gap test and get back with the results. The spark must jump a 7/16 gap.
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  3. #3

    Default Re: carb problem

    Wires were bad , so replaced all electrical. compression was around 150 on all cyl. spark was good on all , rebuild carbs . checked reeds all good.

  4. #4

    Default Re: carb problem

    Wires were bad , so replaced all electrical. compression was around 150 on all cyl. spark was good on all , rebuild carbs . checked reeds all good.

  5. #5
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    3,847

    Default Re: carb problem

    Exactly how did you check the reeds?
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  6. #6

    Default Re: carb problem

    I split the crankcase and used a snake camera and feeler gauge to check reed stops and reeds and reed blocks , all looked like new and checked out to specks.(I am a retired Auto & Diesel Mechanic - Machinist ) checked and replaced all gaskets and seals. Had the carb problem before and still do. Never been inside a outboard before ,Keeps this old man busy & happy.

  7. #7

    Default Re: carb problem

    Are you available for adoption?

  8. #8
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    3,847

    Default Re: carb problem

    Check that the carbs are fully closed and that they open at exactly the same time. Idle speed is dependent strictly on ignition timing. Do you have a manual that explains how to set the throttle pickup. Mercs can be tricky getting the sync and max spark advance. What is the serial number of your motor?
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  9. #9

    Default Re: carb problem

    carbs shutter plates are in sync , have a good service manual , serial no. is 6174797

  10. #10

    Default Re: carb problem

    Depends on how much money you have

  11. #11
    Join Date
    Dec 2015
    Location
    maplevalley WA
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    3,847

    Default Re: carb problem

    Did you say one carb has the slow needle turned all the way in? Possible pin hole in the fuel pump diaphram or damaged float needle?
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  12. #12

    Default Re: carb problem

    lower carb adjustment screw all the way in Fuel pump is rebuilt ,float needle new

  13. #13
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    3,847

    Default Re: carb problem

    Does the primer bulb get hard once fill the carbs.
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  14. #14

    Default Re: carb problem

    primer bulb gets hard , filter is full of fuel. pulled the bottom carb ,full of fuel , cleaned and check in out , reset float found not problems with carb. fuel pressure good. will re install carb tomorrow and recheck throttle adjustments and recheck timing ???????????

  15. #15
    Join Date
    Dec 2015
    Location
    maplevalley WA
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    3,847

    Default Re: carb problem

    Both carbs must be fully closed to adjust the slow needles is the throttle cable disconnected? Loosten the idle stop screw and back off until it no longer touches. Preset the slow needles out 1 1/2 turns from lightly seated. Follow the instructions on how to sync throttle opening to spark advance. Once it is fully warmed up adjust the slow needles in forward gear with a load on the prop either in a barrel or on the water. Point ot toward the big part of the lake and check adjust max spark advance. After each adjustment disconnect the throttle cable to confirm proper idle speed and adjust the cable as necessary. It could be as simple as a cat hair in the float needle your just missing a step. High idle issues are always too much fuel or spark advance.
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  16. #16

    Default Re: carb problem

    Looking at the welch plugs on the carbs got to thinking they may be sucking air so I sealed them with gasket sealer and now the carbs adjust like they should. runs good but still idles around 1000 rpm . could the jets cause the fast idle if the main jet and the vent jet was reversed ????? Thanks for info

  17. #17
    Join Date
    Dec 2015
    Location
    maplevalley WA
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    3,847

    Default Re: carb problem

    Did you disconnect the throttle cable and adjust the idle stop screw?
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  18. #18

    Default Re: carb problem

    Are you testing this in the water or on muffs?

  19. #19

    Default Re: carb problem

    testing in a tank in my shop

  20. #20

    Default Re: carb problem

    idle stop set, throttle cable disconnected, carbs closed all the way ,still can't get below 1000 rpm ,in or out of gear

  21. #21
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    3,847

    Default Re: carb problem

    Did you get the timing to retard? Is the cavitation plate at least 5 inches under water when in forward gear as you adjust the slow needles?
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  22. #22
    Join Date
    Dec 2015
    Location
    maplevalley WA
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    Default Re: carb problem

    Maybe you have a sticking trigger?
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  23. #23

    Default Re: carb problem

    timing calls for 2 btdc to 2 atdc runs best 2 to 4 atdc, still fast , running with out the prop on ,this would cause faster rpm , but would prop on drop it 400 rpm??? cavitation plate is 4 inches under water. How do I test for sticking trigger ? trigger is new

  24. #24
    Join Date
    Dec 2015
    Location
    maplevalley WA
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    Default Re: carb problem

    Is there an adjustment between the trigger and the spark advance lever? Are all the bushings tight well greased and operating smoothly? Sounds like you had it all apart but even if you took picks there is no guaranttee it was correct before you took it apart. Keep at it you will get her dialed in eventually!
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  25. #25

    Default Re: carb problem

    no adjustment on the trigger to spark advance lever, bushings are tight , the throttle cam is a little sloppy but with throttle backed off this would not affect idle.

  26. #26
    Join Date
    Dec 2015
    Location
    maplevalley WA
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    3,847

    Default Re: carb problem

    Is that idle timing in the book or does it say throttle pickup? Yes engine idle can drop 300-400 rpm with a load on the prop.
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  27. #27
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    3,847

    Default Re: carb problem

    To protect the engine and help on cold starts adjust the slow needles for the smoothest lean setting on both carbs the add 1/8 to 1/4 rich. Adjust the needles slowly 1/8 turn at a time and wait between adjustments for the crankcase to stabilize 5 to ten seconds.
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  28. #28

    Default Re: carb problem

    Idle timing is on the cover over the carbs, same as in manual, have a very good manual , came with the outboard in 1982 about 2 inches thick covers modles from 75 hp to 150 hp the manual is probably worth more than the motor. everything is back together the way it should be .

  29. #29

    Default Re: carb problem

    need to run and adjust it on the lake, with 3 feet of snow , and the water is a little hard it'll be a few months, live in Montana. thanks for your input

  30. #30
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    15,324

    Default Re: carb problem

    When the weather clears up--about August!--try running the motor at idle off the fuel tank.: Hook it right to the carbs and GENTLY work the bulb. If it runs okay, replace the fuel pump.

    Hell, you got nothing to do for months so why not just do it now?

    Jeff

    PS: My wife and I just LOVED Montana.

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