Strange material on coil

[Ky Howard]

I’m working on a late 80’s 20 Hp mercury. The coils have a material between the coil body and the rubber shield as shown in the picture. It looks like magnet but it has no continuity. Further the coil ground tab overlays it which would seem to make a connection as if making it a ground. What is the material and what is it’s function? Do cracks and chips in that material have any negative effect on the coil operation

 

[Quicksilver]

It's the ferrite core that concentrates the magnetic field; I think that it will affect the coil's strength. I had one crack up like that and the spark was weakened.

 

[Ky Howard]

Thanks I'll look into changing them