Mercruuiser Exhaust Shutter Noise

[sallen98]

Hello Fellow Boaters I recently had to do some repairs on our boat and while doing so I found that the exhaust shutters in the "Y" pipe had worn and fell out. I had no issues getting the old ones out of the "Y" pipe and replaced with new style with the plastic oval retaining ring frame. My issue is that at around 2000 rpm's I am getting a shuttering sound/vibration on the right side exhaust it kind of sounds like a helicopter I believe that at a certain RPM the shutters hit a harmonic zone that makes the noise. Has anyone else had this issue and how can it be solved.