Hi Again. This board has been verry helpful to me.Thanks all.<br /> Are the flappers in the exhaust system always installed or are they optional.I presume they are to keep water out. My 1997 Volvo Penta 5.7 L gl has the small shafts in the exhaust but there are no flappers ( i'm not shure that is the proper name ) Do I need to replace them or not ?<br />Thanks Bill