I am not familiar with these devises as my previous boats engine was above the water line and did not have any. My current boat has one that looks like it was never removed. I have heard that these must be maintained for them to operate correctly. What must be done to these? I unscrewed the valve and there was a peice of cardboard looking thing blocking the valve air hole. Is this the way it is suppose to be? What should I do?Thanks!GregP36-2