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1977 70hp Evenrude stalls sometimes going from idle to full throttle.

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  • 1977 70hp Evenrude stalls sometimes going from idle to full throttle.

    I'm going to call this one the up north blues, as normally only happens once a year for the week we go up North in WI with family. This week up north we use the boat more then the entire rest of the season. Fish in morning, ski during the day eat and then fish is the daily usage.

    Normally only happens when in gear taking up slack and I gun it to get a skier up or multi-rider tube. We start up the motor, pull away from the dock and after they get settled in the water take up slack and then goose it. I can sometimes nurse it back if I pull back quick but normally they let go and I drive around in a circle to see if warming it up some will help.

    I'm going out with the boat today and will try to see if I can repeat it at home, but wanted to know if others have had the same issue and what they found to be the problem.

    Note I have a aftermarket fuel line/primer.
    Plugs have been changed out and did a de carb procedure with sea foam before last years trip. Did happen less last year but still did occur.
    Fuel pump is original and I am not against changing out but not sure it is the problem.
    fuel lines were all changes several years ago from the pump to the carbs.

    Every season starts up no problem, and works great. And is only a minor inconvenience when it stalls as it does it several times in a row then will be just fine. Problem is my 7yr old is probably ready to get up on skis and I don't want the motor to stall to be the reason he gets frustrated and doesn't get up.

    Any suggestions or tips? I did have someone try pumping the priming pump to see if that helped and I couldn't tell if it did or not at the time as the user wasn't very keen with a primer bulb.

    Model # 70773S

    Thanks for any suggestions.


  • #2
    Re: 1977 70hp Evenrude stalls sometimes going from idle to full throttle.

    Seen it before. Check your throttle stuff on the motor. As you advance the throttle from idle, most of the movement should be the long vertical bar that moves the spark advance. Only when the spark is at full advance should it bury the carburetor throttle shafts WOT. The spark advance bar is moved by a coil spring where it pivots. If the timer is sticky, the spring doesn't move it, and you bury the carburetor throttle shafts at less than full spark advance. That will make it stumble severely, of conk out completely. May work fine the next 20 times.

    Cure: You have to disassemble and clean & re-lube the throttle mechanism and timer base mounting.


    • #3
      Re: 1977 70hp Evenrude stalls sometimes going from idle to full throttle.

      F_R; Thanks for the quick reply, Do you know of any thread that details the steps (I will look around and pull out my non oem service manual)? Also what lube should be used and any specific cleaner?