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?
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.
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.
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.
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.
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!
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?
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.