Magneto Plate Binding

[bobw]

So after resolving the ignition miss problem on my 1972 Evinrude 25hp, I wanted to tackle another issue with a very stiff throttle control action. I first checked the throttle control handle, shafts and gears and found those to be very smooth and easy to move. I then pulled the flywheel and checked the magneto plate and found it to be very tight and hard to rotate. I first checked for any rotational interference from plug wires, kill switch wires or the mag plate grounding wire and found no problem with any of that. Also checked to make sure the attachment screws for the points were not too long and protruding through the bottom of the mag plate and binding on the support plate – they are not. Found that one time on another motor believe it or not.

After loosening the mag plate attaching screws just a little bit, the plate will rotate on the block boss very smoothly and easily. I find no lateral play or slop in the fit of the mag plate on the boss – it seems to be a very good fit. When I reassembled this motor last year I applied a very THIN smear of grease to the retaining ring, to the top of the support plate and to the magneto bushing itself. The retaining ring is installed flat side UP. The problem seems to be when I tighten the mag plate retaining screws, it is sucking the retaining ring up very tight to the support plate making it bind up (see pic enclosed showing rub marks on the top of the retaining ring). I pulled the support plate off and did find that it is not perfectly flat – when checking it with a straightedge there is some distortion or “warpage” so I assume the support plate is just messed up.

When I first acquired this motor I found the throttle to be very stiff but I attributed that to the fact it had been sitting in storage for some 12+ years. I didn’t notice it when I initially dismantled the motor and then reassembled it later but on closer inspection now I see what appear to be some tool marks on the support plate (see pic enclosed) so I assume the PO or whoever may have worked on the motor in the past must have fooled with the plate for some reason. I found a NOS retaining ring and support plate which should be delivered next week, but any other things I should look for?

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

• This topic was modified 5 years, 2 months ago by bobw.

[Buccaneer]

I usually run into the other problem, “loose loose”.
It doesn’t take much of a punch prick to tighten them
up, so assume if your retainer is warped, you found the
problem. Sand down any little nicks in the retaining ring,
and I’d think you’d be good to go. A little patience and
a hammer would probably make the old support plate
usable, but then again, maybe I’m just cheap. 🙂

Prepare to be boarded!

[mark weaver]

I think that retaining ring goes taper UP. That allows the ring to go up through the brass ring about a 1/16 or so and that gives you space between the retainer and the brass ring when tightened to the mag base.

[frankr]

mark weaver wrote:

I think that retaining ring goes taper UP. That allows the ring to go up through the brass ring about a 1/16 or so and that gives you space between the retainer and the brass ring when tightened to the mag base.

Nope, not so. The flat side gores up. I agree, the support ring has been bent by somebody.

[bobw]

I found a used retaining and support ring in good condition, put those in and it worked fine. The old support ring was indeed slightly bent – I’m assuming the PO worked on it to tighten up the throttle action and went a little too far with it. And yes, flat side of retaining faces up. Sold this motor some time ago and new owner tells me it’s still running strong.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

[fleetwin]

Yes, someone got a little aggressive with the “prick punch method” of tightening up that retaining ring….But, I have also found some of the new hardware included with OEM coil is just a tad too long and rubs on the retaining ring as well….

[Author]

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