I'm the worst about being hypersensitive to strange noises when in a boat. It tends to happen when you have gone trough as many motors as I have. Those flappers sound just like a bottom end knock. The first time I installed them I also rebuilt the motor with some major upgrades. After the first start I was almost ready to pull the motor back out of the boat until I figured out that it was the flappers. After a summer of that dredged noise I cut them out with a saw-zaw and put the rubber flappers back on the ends.

Agree I stuck a broom handles in mine and changed the name of the boat to witch

I have both internal flappers and external mounted on my Gibson clamp on mufflers. I believe the mufflers also help prevent reversion, can't be too careful, especially when you boat in the Great Lakes. The fresh water has lower surface tension then salt water and the waves are closer together, you can get buffeted pretty good. If you can hear your flappers your engine isn't loud enough, LOL.

Don't think I have that problem.

https://www.youtube.com/watch?v=3hxWh-Zhp_8

Yes they do ! stick with the external rubber ones !

You need more cam in that thing! LOL I need to find out what kind of internal flappers I have, I don't hear them at all even when I get into the engine compartment.

What do you think about these? Going on a 27 fountain with a HP 500 wipple charged with stock manifolds.

http://www.cpperformance.com/p-12592...haust-tip.aspx

I burnt the rubber out of my S.S.M. tips last summer when I lost a water hose and overheated the tips. I called S.S.M. and it's going to cost me about $80 a tip to have new flappers installed because they don't just replace the rubber. It's worth the money to me though because without the rubber the flappers are sticking shut until I'm in the throttle. Which could push water back into the exhaust ports. Not worth the risk IMO.

MHO get the straight cut bc u can get yourself a big cut on your hand or leg or.......call Eric at teague

What about reversion?