1993 johnson 112 outboard will only run at idle speed

Discussion in 'Outboards' started by redsnap 1070, Mar 10, 2014.

  1. redsnap 1070
    Joined: Mar 2014
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    redsnap 1070 New Member

    Gentlemen and ladies
    My 1993 johnson outboard dies down whenever I try to get going ...It will pick up for a minute then all of a sudden it will die down..and if I don't back off the throttle it will cut-off completely. So I have to ease along at just above idle speed to get home..I have changed out the fuel line and have made certain all the filters are clean..I use etanol free gas...I am at wit's end..any advice would be greatly appreciated
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    It always helps to have a workshop manual on hand, to troubleshoot these problems. You could check the fuel pump for faults, and there is a gauze filter in that too. The diaphragm can perforate and not pump properly. It is a relatively simple task to dismantle and check out.
     
  3. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Have a helper squeeze the ball when the engine bogs down. If the engine responds again, the cause is fuel starvation. Notorious places are the fuel line socket and the internal hoses. A tiny leak allows air in the fuel line, reducing the pump's capacity to feed the required amount.
    If there is no leak and the fuel tank vent has been checked, this probably is a carb problem, requiring the carbs to be removed and thoroughly cleaned.
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    Good advice, he'll probably need a helper to squeeze the bulb while he drives the boat, otherwise if solo he can elevate a tote tank higher than the engine and gravity feed it fuel.
     
  5. whitepointer23

    whitepointer23 Previous Member

    sounds like fuel pump.test as advised above.
     
  6. FAST FRED
    Joined: Oct 2002
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    FAST FRED Senior Member

    Sounds like crap in the large jet for above idle operation.
     
  7. 7228sedan
    Joined: Nov 2009
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    7228sedan Senior Member

    I second Fast Fred did you go through the carb(s)?
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    Obviously he has put an axe through it, and won't be replying. :D
     
  9. Dave T
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    Dave T Senior Member

    Sounds like a fuel supply problem to the carbs most likely fuel pump. Usually if it's a plugged main jet in the carb the motor will die as soon as you open the throttle but since it revs up first and then dies out it indicates that there is not enough gas being pumped to the carbs. The fuel bowels are being filled when the motor is idling which lets the motor first rev up but there is not enough fuel getting to them to keep them filled. The best way to check the fuel pump is to remove the line from the pump that goes to the carbs and connect it to a small tank so you can gravity feed it to run the motor and check the volume pumped and fuel pressure from the pump
     
  10. Dave T
    Joined: Sep 2011
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    Dave T Senior Member

    Another thing to check if the boat has a built in fuel tank, check the fitting where the fuel hose connects to the tank. We ran into this on a friend of mines pontoon boat. The fitting was aluminum and had a check ball built into it. The aluminum had corroded and the check valve was only opening part way and restricting the flow and the outboard motor was doing the same thing as yours. We removed the fitting put it in a vice and used a punch to knock out the check ball, spring and seat and then reinstalled the fitting in the tank. The check valve is only needed if you have an inboard motor as an outboard has check valves in the squeeze bulb
     
  11. powerabout
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    powerabout Senior Member

    thats an anti syphon valve and is a requirement if any part of the fuel system is below the top of the tank, and yes a common source of problems
    A primer valve cant do the same job
     
  12. SukiSolo
    Joined: Dec 2012
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    SukiSolo Senior Member

    If you have ensured the fuel supply and pump are OK, I'd second cleaning the carb. When carbs are left and dry out ie in winter when engine laid up, quite often a scummy deposit from fuel can get deposited on the idle mixture screw end and in the channels. Quite often cleaning this out resolves the problem. Be aware that the mixture screw is set usually something like between 1 to 3 full (360 degre turns) out so to remove it, first tighten it counting the turns to lock solid in. Then remove it clean, preferably with carb cleaner and replace to original setting by counting the turns back from the solid locked in place point.

    Worth removing the float bowl and cleaning needle valve and chambers if you have removed the carb. Squirt through all the orifices that are used and remove and clean any other internal jets and atomisers. Check the float itself too, make sure not punctured or leaking. On my 20+ year old car the float was 0.5 grams too heavy because the plastic had absorbed fuel over time, and yes it was sensitive to even that small ammount.

    Small outboards and especially 2 stroke are the most prone to the build up of the brown/amber sludge from dried out fuel but it can affect larger ones too.
     

  13. powerabout
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    powerabout Senior Member

    redsnap
    can you post a photo, it is a crossflow v4 with 2 twinbarrel carbs I assume?
    or the model number
     
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