1961 40hp Evinrude difficult to turn under compression

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  • April 26, 2023 at 1:58 pm #275632
    pinka

      Thanks all for the help.  My next steps are check, clean and lube the starter.  Make sure I have a properly rated battery.  Sheepishly, that could also be an issue.  Does anyone know offhand how many CCA this engine would require?

      I know the wires in the harness are old and brittle as well.  If it weren’t for the sheath that they are in, I am sure they would crumble. The harness is on my list to rebuild.  Currently, I am working around it and the solenoid with jumper cables.

      April 26, 2023 at 2:10 pm #275633
      Finn Freeman
      Participant

        US Junior Member
        Mumbles wrote:

        Something doesn’t look right in your first photo as there is no compression relief at all on that cylinder head. The only thing I see is the hole on the rewind starter for the pivot pin for the valve linkage. Either the head has been changed over or the whole powerhead has been replaced at one time.

        Look on the block for a welch plug with some numbers stamped on it. It’s about the size of a quarter and might be on the top of the block. The numbers should match the ID plates numbers which is mounted either on the front or the sides of  the transom clamps.

        1961-Rude

        Mumbles, I think that the cavity in the rewind starter is there for any of the big twin engines after 1957. I have a 1962 28hp that has the hole for the compression relief in the rewind, but the 28s and 33s didn’t have the compression relief. It is probably much cheaper to use 1 casting instead of 2.

        April 27, 2023 at 10:32 am #275653
        pinka

          I pulled apart the starter.  It was very gummed up inside. There were only two brushes. One of the brushes was stuck.  I freed it up cleaned everything out.  I lightly sanded the surface the mild corrosion off the armature. Cleaned the communicator. Put a little lithium grease at the base of the spindle and reinstalled.

          I connected it to a 700CCA battery with jumper cables and while it was a little better, it still didn’t have enough oomph to keep the flywheel spinning without pausing for a moment.

          The brushes were worn.  I am not sure how worn is worn out. They were worn to the shape of the round communicator.  I would guess from looking at photos of new ones that they were at least a 1/3rd worn down.

          The other thing that happens now is that the gear doesn’t retract when the starter stops spinning.  It wasn’t doing that before I took it apart.   I’ll take it apart again and post some photos tonight.

          April 27, 2023 at 10:42 am #275655
          fleetwin
          Participant

            US Member - 2 Years

            OK, well the book shows that the compression relief was still used in 1961, which is the year I’m guessing at based on the engine cover.    Those head bolts look messed with, so the head could have been swapped with a later model that does not use this feature.  One thing to keep in mind is that the compression relief is not activated when the electric starter is used, so it has no effect when cranked with the starter motor.

            OK, you cleaned up the starter, which improved things slightly. Are you sure the battery cables are in good shape?  Are you using jumper cables or the cables in the engine harness?  Might be easier to just try another starter motor….

            April 28, 2023 at 12:15 am #275693
            pinka

              I heard a beautiful sound tonight.  I don’t know about size, but AWG does matter.  I pulled out a heftier set of jumper cables and she turned over quickly, smoothly and quietly.  The wire harness also had no problems cranking.  My compression topped out at 100 in both cylinders.

              I will put the lower unit back on this weekend put her in barrel of water and see how well I did at cleaning and rebuilding the carb and rebuilding the water pump.

              I am still not sure what year the power head is exactly.  It is definitely not a ’61 but I can’t find any other numbers on the power head.

              April 28, 2023 at 4:33 pm #275715
              fleetwin
              Participant

                US Member - 2 Years

                Cool!  So happy you have sorted it out.  Don’t worry about the compression relief system, or the year of the engine.  Get her running and enjoy it.

                PS:  Looks like the 1962 models did not use the compression relief system, I was just basing my comments off the engine cover in your picture, which is from a 1961 model.

                May 1, 2023 at 11:56 am #275789
                pinka

                  Thank all for the help!  I learned a lot.  I think I will consider this compression issue that never was closed.  If more issues crop up that I can’t solve, I will make a new specific post.

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