Tower Mirror Vibration

Does anyone have any suggestions on how to dampen the vibration of the mirror mounted on a '05 216 Sport Nautique's tower (standard factory supplied arm)? At certain speeds, the vibration makes the view blur.

The prop is not dinged but could be the issue, as well as anything out of balance. The frequency happens to be at wake boarding speed only @19.5 MPH. It could also be just one of the natural frequency speedi issues of the drive train that occur. Manufacturing equipment that I have worked on are sometimes prevented from running at speeds where vibrations occur - that's why variable frequency drives have "skip freqencies". If dampening out this vibration cannot be done, I will taking it in to have it looked at.

matchbook....seriously you could of scraped some sand and would never know it I would go after the prop first, the boat should be smooth at all rpm ranges, remember the prop spins engine speed unless its a 1.23 and that is very fast.