If you have tried every test known to man and can't find the air leak try this. Remove the 4 bolts holding the plastic bowl. Remove the bowl. Spin off the turbine. There is a small metal ball and gasket inside the turbine tube. The gasket is made by a company known as TOP. THe gasket comes in a package that says TOP. Sometimes people think that indicates how the gasket is to be installed. It boggles the mind to think that this is the cause of anyone's air leak, but I know of a boat where this is exactly what bit me. There are two distinct sides to the gasket. 1. A flat surface with a hole. 2. An indented surface. The ball sits in the flat surface side. NOT the indented side. Let me know if this solves anyone's problem. The fellow who provided this info would like to know if this a prevalent problem. Mike +++++++++++++++ Capt. Mike Maurice Beaverton Oregon(near Portland).