Is your prop Sharpened & Balanced or Stock??
All props must be Sharp and extremely well balanced and even then they will wobble more at certain RPM's than others, especially at low RPM's and Out of the water with No Load on it or the flex shaft.
Its the stock plastic prop. I have a grim prop, the one recommended in the manual on the way that should be here today. I have the Top flight balancer pictured here...
http://www3.towerhobbies.com/cgi-bin...XHY61&P=ML
but i was unable to get the stock plastic prop to balance on it because it was so light, the magnets attraction to the balance rod stoped it from spinning before the prop would really have any effect on it. That rod is at least 2-3 times as heavy as the plastic prop. Now i have not lapped the faces of the magnets yet, so maybe that will help.
ALWAYS Twist the flex shaft "Clockwise" as you remove and install it (like your trying to wind it up tighter). A tight fit in the coupler is Much better than a Loose fit. <span class="info"></span>
Yeah, i figured that was the best way to do it. And i agree, a tight fit is better than a loose one.