1961 40hp Evinrude difficult to turn under compression

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  • April 25, 2023 at 2:01 pm #275587
    pinka

      I am trying to resurrect this motor and have run into a problem.  When the plugs are out everything turns freely.  I can pull the recoil easily.  The electric starter can spin the flywheel easily.  As soon as I put the plugs back in, it is very difficult to pull.  The starter also has trouble and will turn and then hang up and then turn.  I have the lower unit off at the moment.  I also pulled the exhaust housing.  It was clear.  The flywheel is still has a lot of resistance when the plugs are in.  When a piston clears the exhaust ports it gets a little easier but not as easy as when the plugs are removed.  What could be causing this?

      History- It is a barn find.  Owner says it ran 15 years ago but the coils were cracked and it was shorting out.  The magneto and flyweel were off and the motor had the cover on.

      1. Compression is 90 in both cylinders hand pulled.
      2. They cylinders look smooth along with the bore.  I cleaned the piston heads and and replaced the head gasket.
      3. I rebuilt the magneto. Coils, points, condensers, plug wires, spark plugs I get spark from both plugs.
      4. I rebuilt the carb with a kit and replaced all the hoses.
      5. Inspected lower unit.  Replaced the shift lever in the lower unit that was corroded. Replaced the water pump.  Replaced the seals and sealed it back up.

      So, I am committed to this engine at this point. I would appreciate any help that anyone can provide.

      April 25, 2023 at 2:39 pm #275588
      frankr
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        Well, that is a tough question to answer.  It is supposed to be hard to pull over compression.  Are the compression relief valves working?  You had the head off and didn’t see any obvious damage, so I assume the bearings, etc are not trashed.

        Barring any additional information, I have to guess there is nothing wrong with it (????)  Except for a weak electric starter, that is.

        April 25, 2023 at 3:06 pm #275589
        frankr
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          Tell us more about yourself.  Are you a big strong person or a skinny teenager, or what?  Is the motor mounted on a boat, or on a stand?  It would be very difficult for an average person to pull it over if  on a stand, or whatever if not securely held down.  Even if mounted on a boat, you would have to stand ahead of it, grab the rope with both hands, and haul on that rope. I’ve seen skinny teenagers able to start them and a mom that can pick up a 50 pound kid with one arm, but just can’t rope over even a small outboard. No insult intended, just say’n.

          April 25, 2023 at 3:30 pm #275590
          pinka

            Thanks for your reply.  Let me just say, I am new to this so I am not sure what normal is.  My model is 35525.  I have been searching and reading everything I can.  I am not a hulk but it seems like the resistance is stronger than it should be.

            I pulled the cylinder head but that only allowed me to see the tops of the cylinders and the bore walls.  I have not seen the crank shaft or cam.

            I just looked up the “what and where” of the valve you mentioned.  Is it in the cylinder head itself?  I didn’t see it or check it when I changed the head gasket.  Do I need to take the cylinder head off to check it. How do I know whether it is functioning properly? In the diagram it looks like there is an o-ring as well associated with it.

            Thanks!

            April 25, 2023 at 3:47 pm #275591
            pinka

              I am 6’0 and 50 years old.  I do have the motor on a stand. I can brace the stand with my foot. It is on locked wheels but it can move.  I can get it to overcome the first compression but the second one stops me most of the time. I will try to brace it.

              Perhaps the starter is weak or I just need more leverage. After playing a with the flywheel and the plugs out, I can also see that the flywheel is dragging on one of the coils a little bit and is pulling on the plate.  Perhaps the friction is adding up as well. I did read somewhere where the old plates can wobble on the stator.  I will check it out later.

              Thanks for the thoughts, suggestions, and questioning my manhood. 😉  Sometimes it just helps to know what is normal so I don’t go fixing things that aren’t broken, yet.

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              fleetwin
              April 25, 2023 at 3:53 pm #275593
              frankr
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                Look at the outside of the cylinder h.ead,  See those two lumps next to the spark plugs.  Those two boxes, let’s call them, are closed containers, nothing inside them except air.  Next to them you should see two valve stems with springs around them.  When you pull the starter rope, the valves should be depressed.  That adds the volume of air inside the “box” to the volume of air inside the compression chamber.  Since the pistons are compressing a fixed amount of air into a larger total chamber volume, the pressure will be reduced (relieved somewhat).  When the rope retracts, the valves close and normal compression returns.  Bottom line, are the valves opening when you pull the rope?

                April 25, 2023 at 3:58 pm #275594
                frankr
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                  I just looked at your picture.  The compression relief linkage is completely missing.  My manhood is “nowhere” what it used to be, but even in my prime, I would have had a hard time roping that thing over on that stand.

                  April 25, 2023 at 4:08 pm #275595
                  frankr
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                    Another thing:   Even if bolted to the floor, it would be difficult to pull the rope with the starter so high above the floor, no matter who you are.  Mounted on a boat, it would be much lower and you could throw your body strength into the pull.

                    April 25, 2023 at 4:56 pm #275597
                    pinka

                      Interesting, I have see images of the 35524 powerhead and noticed that the back looked different than mine with some kind of lever and other caps protruding from the back.  But I have seen other images of this motor and they look similar to mine with out the relief linkage.  I don’t see any clear signs of missing parts that were once bolted on.  When I look up the diagram on marine engine, I see the additional parts but I don’t see where they would go on the head.

                      I don’t have a clear picture of the back on my phone.  I will try to get one tonight.  When I found the motor, it looked like this.

                      April 25, 2023 at 5:20 pm #275599
                      jeff-register
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                        US Member - 2 Years

                        P.S. There isn’t a cam in your motor except on the compression release & it’s missing. That’s a big bore motor & hard to rope over. If it was me I would get a good starter for it. Wait till it kicks back once, it will pull your shoulder out.

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