Flaps in exhaust?
 

Last night I noticed on my 4" standard thru hull exhaust, (not tips) that there is little holders inside the tubes that maybe should hold the internal flapper. Should they be something in there since I use the external flappers and my exhaust is a few inches above the water?

They are suppossed to have internal flappers but I don't think you need them if you are useing external. The internal flappers do wear out and will fall off if you don't replace them. My friend found out the hard way, had a wave dump water down the exhaust because he did not notice the flappers had fallen out.

Did boat come with external flappers ? If not sometimes they use the metal internal flappers . People take them out because they are a little noise at idle and put on rubber external flappers . Just a thought. I would put them back in . Better to be safe then sorry.

The boat had external flappers, but I still don't like the way water goes up the exhaust when the boat is resting near heavy boat traffic. Think I will add them back.

Why not both ??