the small round doughnut type rubber that you have is definitely not the rubber for the mount the proper rubber has a smooth face and a face with a series of bumpy bits around it, the rubber is placed between the body work/rearpanel and engine mounting plate to stop the two striking together, its most likely that the original has been worn out from doing lots of work, is it particularly bumpy where you live? i would get a pic of the original but i dont have any to hand at the moment as i need a sort out. try putting the doughnut you have where i have described and you should see a big difference.