Both of the exhaust flappers in my y-pipe are missing in action. I can not find the exhaust system parts on mercruiserparts or any other sites. This is a 91' setup with the one piece y-pipe. I found one of the flappers stuck in the lower part of the pipe and they look to be just a one piece flapper. Does anyone know the part number for these I will try to upload a picture later on if that will help. Also where I run with the Merc style silent choice through the transom 95% of the time do these y-pipe flappers serve their purpose?