Topic: Wear/looseness in mag plate bearing – Antique Outboard Motor Club,Inc

This topic has 13 replies, 10 voices, and was last updated 5 years ago by Steve D.

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April 4, 2019 at 6:27 pm #172622
olcah
Participant
US Member
Every OMC mag plate I have worked on has looseness in the bearing if you lift the edge of the plate up and down. Lift up/push down definitely changes the points gap. Wear would increase this play. I expect that to cause the points gap to change when the motor is running. Usually I just time with a ring at throttle midpoint and ignition works fine. But how much play is too much? Short of replacing the plate with NOS is there a fix? Wondering what others think about this?
- This topic was modified 5 years ago by olcah.
- This topic was modified 5 years ago by olcah.
April 4, 2019 at 9:25 pm #172640
olcah
Participant
US Member
I broke down and bought a NOS mag plate as the best plate I have seems extra loose. Still interested in anyone’s thoughts on this problem as looseness of the mag plate bearing seems very common.
April 5, 2019 at 8:12 am #172662
frankr
Participant
US Member
There are kits to update some models to better mounting system if you have a motor that you really care about. Sorry, I’m off camping and don’t have the part numbers with me.
April 5, 2019 at 10:19 am #172670
lloyd
Participant
US Member
You can make a bushing out of thin brass sheet (shim stock) and mount it inside the mag plate hole. I have done it before and it worked for me.
April 5, 2019 at 10:40 am #172671
jeff-register
Participant
US Member - 2 Years
I have had electrical grounding issues with loose mag plates too. Be sure to run a bonding wire from the plate to the cylinder block, it helps!!
April 5, 2019 at 10:43 am #172672
chinewalker
Participant
US Member
I’ve tightened up a few by dimpling the bearing surface on the powerhead with a punch. Two dimples, vertically, at all four points of the compass, eight dimples in all.
April 5, 2019 at 3:04 pm #172689
frankr
Participant
US Member
For anyone interested, the update kit is part #580871.. It is specified for 28-33-40hp motors but will fit a bunch of others by maybe drilling/tapping a missing hole or two.
April 5, 2019 at 5:01 pm #172691
chris-p
Participant
You can get the kit Frank mentions, or simply dimple the brass bearing surface. I do a LIGHT tap with a punch every 90 degrees, 4 total. Just light, it really tightens it up!
April 6, 2019 at 9:40 am #172719
joecb
Participant
US Member - 2 Years
Frank, what does the ” the update kit is part #580871.” consist of? a whole new mag plate? or just the brass insert ? Is any machining work needed for truing a worn boss on the crank case?

Joe B
April 6, 2019 at 10:45 am #172725
seakaye12
Participant
US Member
Here’s a Picture of the “dimpling process”. It’s a picture that has been floating around the internet for years. I’d love to give credit to the author but I don’t know who it is.
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