I just found an OMC 6 gal tank for Evinrude/Johnson at a local dealer that has the OMC fitting on it, a gauge, and the cap has a rubber ‘duckbill’ on the underside which he tells me will let air into the tank, but not out of the tank. So I’m going to see how it goes.
That “duckbill” is what I clipped. Before I clipped it, it would let air in but not out so it swells!
