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1997 Johnson 15HP armature plate/flywheel problem

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  • 1997 Johnson 15HP armature plate/flywheel problem

    Installing the flywheel is literally the last step before test firing this motor, and when lightly tightening the nut, it is binding on something and will not rotate. I'm wondering if I have the armature plate and support ring installed correctly? The support ring can really only be mounted one way due to how the screw hole configuration aligns with the holes in the powerhead. When I place the armature plate assembly onto the top housing of the powerhead, the 2" I.D. brass sleeve center hole on the plate assembly only seats down approx. 1/16" or so. The thickness of the sleeve is 1/2" so only a small portion of it is actually making any contact with the upper crankshaft housing.

    The crankshaft rotates fine when using only the flywheel nut and a wrench, and the plate assembly when seated, turns very smoothly also. It "looks" like the plate assembly should be seating lower onto the powerhead, but I failed to notice this when I took everything apart. I've done all the engine work up to this point with the plugs out, and only after re-installing the plugs did I attempt to attach the flywheel. I thought maybe that was causing the binding, but after removing them it's doing the same thing.

    Hopefully someone here has run into this same problem, because I'm about out of ideas. Just to add, when tightening the flywheel nut, I'd give it a half turn and then rotate the FW. After the nut is just snug, the binding occurs within 1-1/2 full turns of the nut, so I never really tightened it much at all.

  • #2
    Strange indeed.-----Everything out of the way when lowering stuff down.-----Carburetor roller interfering ?


    • #3
      Carb roller does catch on the plate when seating, but I just push it back with my finger (for about the 50th time). I know this wasn't an existing problem because I did use the motor 3X.


      • #4
        I have done more than one.---No problems.-----Post some pictures of the stuff under the flywheel.----Factory flywheel key ?----Key installed the right way?


        • #5
          I'm not familiar with the 1997 model due to retiring and my books only go up to 1992.... should the armature plate assembly be identical, or close to it, I'd suspect.................

          Either the nylon bearing was not compressed properly which would have the retaining ring NOT secured properly (armature plate cocked)... OR... one or more of the armature plate components are NOT aligned properly with the top inside bevel of the aluminum seat upon which they sit which would result in a incorrect distancing of the component(s) from the flywheel magnets.
          Our Questions Require Answers... If You Refuse To Answer Our Questions... How Can We Answer Yours?


          • #6
            My daughter is going to come by in a couple of hours to take some pictures and help me post them on here. I have to say I'm rather computer illiterate... I don't even have a cell phone in fact. As far as I know the key is factory, but then I only acquired the motor last summer. It was formerly owned by some lodge up in Wisconsin...part of a small fleet of fishing boats for vacationers. I can tell that someone had done work on it before, but not sure how experienced. This is my first go at this, and I've gone slowly and researched everything I could find.

            The nylon bearing, if anything, is already compressed too much and will probably need replacement. It hardly has any gap at all left. The support plate fits flush and level onto the powerhead, and the armature plate seems to slide right down into its place...just not far enough. It's really hard to see underneath the plate, but I don't notice anything that would cause interference.

            I do have to hold the plate down with my finger when lowering the flywheel or the magnets will just lift it off of the housing. I have not touched any of the ignition components mounted to the top of the plate, since this project started out as an engine rebuild. I'll get to the ignition system after I try starting the motor if necessary.

            BTW the reason I started this project in the first place was due to compression readings of 45 and 48 PSI. and the sudden loss of 80% power at WOT. When I sent the head to the machine shop to get resurfaced (I also sent the block, crankshaft, etc.) they told me that the engine actually looked pretty good overall. The head was warped .008 however.

            I really appreciate all of the helpful comments, and hopefully I'll be able to post some pictures in a few hours.


            • #7
              When you install the flywheel the magneto plate stays in place !!-----So you have installed some parts in the wrong order.-----Without being there it is hard to instruct on the correct order of parts !


              • #8
                Thanks, I'll go check that. Does it attach with screws/bolts?


                • #9
                  Yes it does.------It attaches with 5 or 6 screws * captured screws " found near the outside edge.----I suggest you wait until picture are posted here.---You do have the plate installed below for this I hope and the retainer for that is properly installed too. ----This can get expensive.


                  • #10
                    I have the parts installed in the following order starting from the powerhead and going up. Part #s are OEM #s :

                    Support plate bearing #322435 encircling the armature support plate #322102. This is fastened to the powerhead with 4 screws. Next the retainer #0338215 which sandwiches the throttle cam to the ignition plate & sleeve assembly #582417. This is attached with 6 thin headed bolts screwing down into the retainer. I'm pretty sure that's the order in which they were removed but not 100% positive of that.

                    My daughter should be here in a half hour...or so she says.


                    • #11


                      • #12
                        The armature support plate you installed with the 4 screws is NOT the first item to be put in place !!!-----See those 5/16" head screws on the outside .-----Undo those and the lower half of the magplate is installed before before that retainer with the 4 screws.-----Do not overthink this.
                        Last edited by racerone; February 8th, 2019, 04:10 PM.


                        • #13
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                          Thanks so much racerone. It worked like a charm...now ready to test tomorrow.