I have an Optimus 55/155 marine stove. The o-ring is at the bottom of the pump tube--it slipped off the pump. I can see it down at the bottom of the tube. Any suggestions on tricks or retrieve it? I am a little afraid of unscrewing the tube. I cannot get a good grip on it and it appears to be thin metal. I don't want to break o crush the pump tube. Thanks for your help.