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magneto plate

R

RGP

Regular Contributor
1958 35 hp Johnson Javelin

Mag plate has a lot of play in it. Axial and radial play. When motor runs you can see it bounce around and hear it "clacking".

Have tried changing out support and ring with used replacements. No difference. Have tried fitting used replacement mag plates. A bit of an improvement but still play.

Is it possible that the crank collar on the block is worn?

How much play is "normal" ?

Thanks
 
(Magneto Armature Plate)
(J. Reeves)

If the armature plate has a a loose fitting, wobbling motion (the plate that the points, coils etc are attached to), it is usually caused by a slightly worn support ring. This allows the point setting to change erratically as the armature plate turns.

The cure is to remove the armature plate so that the support which is attached to the powerhead with 4 screws is visible. Then, with a screwdriver and hammer, or some tool of your choosing, and looking straight down at the support ring, make a slight indentation at what would be called the 12, 3, 6, and 9 O'clock positions. Install the armature plate and check for a smooth turning wobble free movement.


You may need to do that procedure a few times to obtain the proper fit (not too tight, not too loose), but it's worth the effort.

Use a small amount of anti corrosive grease between the aluminum ring and the brass support plate and also on the brass bushing of the armature plate when all is well.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
 
Thanks all.

Joe, regarding paragraph 2: support ring with four screws. Yes, got it in sight. Actually replaced it with used part, no real change. By slight indentation you are saying to hit it, in order to give it a slight deflection downwards, towards the block?
 
RGP said:
Joe, regarding paragraph 2: support ring with four screws. Yes, got it in sight. Actually replaced it with used part, no real change. By slight indentation you are saying to hit it, in order to give it a slight deflection downwards, towards the block?
Click to expand...

Yes, that's correct, just a sight indentation... and when you get it exactly where you want it, it'll last at least another 45 years if you intend to keep it that long.
 
There is an armature plate kit that will greatly improve that looseness condition. It improves the up and down movement as well as the sideways movement caused by a worn neck on the crankcase. It includes a new armature plate and different kind of mountings. Ain't cheap. It would take me awhile to find the kit part number.
 
Of course the crankcase neck wear has something to do with it. That's why they came out with the kit. I've changed out a lot of them back in the day. Sorry, I haven't found the kit number yet, but it includes #'s 10, 12, and 20, and a new modified armature plate. #12 is taller than the original brass bushing and fits lower on the neck, on un-worn material. http://www.marineengine.com/parts/j...cturer=Evinrude&section=Crankshaft+And+Piston
 
Last edited:
Thanks everyone. Great information.

Tried indenting support ring. That took out all the up and down movement that had been present. However there remains quite a lot of side to side play.

I am going to try a few different, used, mag plates I have and see if condition improves.

I suspect that the crankcase neck is worn.

Will update.

Thanks again.
 
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