I've been running the IMCO Powerflow exhaust for 10+ years. It uses the IMCO 4" internal rubber flappers. I've had to change these things out very often. They will end up breaking one of the flaps off, and it goes into the front end of my mufflers. This last set only lasted 50 hrs. Anyone else have these with similar results? I'd go with a different brand if I knew they would last longer.

I found my Imco flaps were broken in my 2004 Nordic. I too looked for a better alternative. I just removed them and haven't had a problem with water entry.

Not sure what formula used in conjuction with their silent thunder boxes but the tips that came through the transom had internal flappers that were all gone which I pulled them off. I run the external flappers now.