1958 Evinrude Big Twin won’t run full throttle

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  • March 26, 2018 at 2:44 pm #9496
    rvdriver
    Participant

      This issue just started at the end of last year. It idles great, but when I add power it runs up and then comes back and eventually stalls. Not sure what the issue is? Air, fuel or spark? Does the carb have 2 jets….idle and high speed?

      Thanks for the help!

      Steven Vale
      Lake Granbury, Texas

      March 26, 2018 at 3:51 pm #73068
      Mumbles
      Participant

        The carb doesn’t have any jets, instead it has two adjustable mixture needles. The two knobs on the front of the motor are for adjusting the carb. Upper knob is for slow speed and the lower knob is the high speed needle. The high speed nozzle in the carb could be plugged to. If the fuel system checks out and builds pressure in the tank, it could be your coils, or condensers, especially if they are original. They break down over time and as they heat up, they quit working.

        March 26, 2018 at 6:41 pm #73074
        chinewalker
        Participant

          US Member

          Make sure the needle valves don’t move of their own accord – issue with the packing/packing nut.

          Make sure the throttle advance rod that rides on the timing advance arm is set properly and gives you full throttle opening.

          Make sure you’re running on two cylinders. Sudden jump from lots of power to very little can indicate an intermittent spark issue.

          March 26, 2018 at 9:25 pm #73081
          fleetwin
          Participant

            US Member - 2 Years

            Well, you have to figure out whether your problem is spark or fuel related…Does the engine run/rough/misfire/drop a cylinder before stalling, or does it just sounds like it is running out of gas and stalling out….Have you tried opening the high speed needle (lower one) just 1/4 turn out?
            Can the engine be restarted immediately afterwards without fussing or priming the fuel tank again? You could have an assistant continually push the primer button on the fuel tank while accelerating/running at high speed to see if there might be a fuel supply/pressure tank issue.
            Start with the basics, such as fresh fuel/oil supply. Water in the fuel will cause the symptom you describe. There is a little filter/bowl that should be checked also. Check the glass filter bowl for signs of dirt/water. The mesh filter element may need to be replaced. You could always try running the engine with the filter removed temporarily to see if that makes a difference.
            The engine could be stalling out due to overheating, does it smoke/steam/appear hot when it quits? Are you sure you have the correct fuel/oil mix? The correct mix is 24:1 for this engine, 1 quart of TCW3 outboard oil to six gallons of regular fuel. No/not enough oil will cause the engine to seize up/stall out after running at high speeds for less than a minute.
            Any chance of posting a video of the engine misbehaving?

            March 27, 2018 at 12:56 pm #73107
            rvdriver
            Participant

              Thanks for all the thoughts and advice.

              The engine was "gone through" before I bought it last year including the fuel tank. I understand now how the carb operates.
              It’s still running on both cylinders when it powers back before it stalls. It’s pretty easy to restart.it only smokes when we start it up for the first time.

              I’ll check the throttle advance arm, the fuel bowl filter and just start again with fresh fuel. I am running the correct oil mixture. I’m hoping a simply adjustment of the mixture neddle does the trick.

              I need to figure out how to post a picture or video to my post. This is a mahogany 14 foot speed at that I built with a neighbor that I’d like to share with the club.

              Thanks again.

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