Hay lew ,me again ,i amnot sure what you have there .when i replaced my muffler's,and every thing else Iused a flanged thru hull with a flapper on it.Idid not stick the fiber glass pipe thru the stern i cut the pipe a few "short and i stuck a piece of exhst hose on it then i pushed the flanged exhst piece in from the out side gooped it and put the screw's in.(now!if you changed the size of the pipe that could be another story sorry i did not reply sooner but now i have to travel to finish my egg slobber jim