Best I think you can do is get some two part 24 hour epoxy, mix enough extra. Clean the coil cover out, scratch the coil cover insides up with some sand paper. With all clean and dry, find a good spot for making a mess. I've saved a few coils like this that were cracking and splinting. These will never come apart and no sand will every get into the coil cover for it is fully sealed and can take some hard knocks in the rocks.
pour the epoxy mix into the coil cover, let it set for about a hour then slip in the coil. With waiting an hour it gets a chance to get a little firmer. If you don't feel comfortable with that just do it right away..It will come shooting out of every opening, I'll let that dry 24 hours. then come back and mix up a little to fill in the spots that require more, which is rare but does add to the sealing. So now you have a coil that is indestructible. But take care of that coil cable also by keeping it siliconed a least once a month and before storing away load it up...