The wrench Alan is suggesting works well. But will slip once the casing is squeezed in. We use them in our service center everyday. The Phillips head screwdriver would be the last resort to use in my opinon. The casing can tear on you and now you have a jagged edge of metal to deal with. Not good. Understand there isn't much room to swing the wrench. If you can, try a large pair of channel lock pliers, if room permits. You only have to move it just a little at a time. There is another filter wrench that we use that has steel jaws on springs, that tighten when you turn it on a 3/8 rachet. Works great for this situation. We get it from either Snap On, Cornwell, or Matco. If you haven't gotten it off, I will see who has it and get back to you. Follow the other sailors advice in replacing the new one. Hand tighten only. Good Luck.