Wear/looseness in mag plate bearing

[olcah]

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 6 years, 10 months ago by olcah.
• This topic was modified 6 years, 10 months ago by olcah.

[olcah]

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.

[frankr]

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.

[lloyd]

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.

[jeff-register]

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!!

[chinewalker]

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.

[frankr]

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.

[chris-p]

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!

[JOSEPH BRINCAT]

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

[seakaye12]

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.

[Author]

Posts