Hi, Boaters
When I spin the prop by a hand to see if the flex shaft wobbles near the coupling, I do not see any wobble and the flex shaft, coupling, and motor are in the straight alignment.
However, around the half throttle, the flex shaft wobbles with vibration, and then, at the higher rpm, wobbling and vibration are much decreased.
What causes this? What will be the solution for wobbling and vibration at the mid-rpm? Advanced boaters' advice will be greatly appreciated. Here is a picture of the boat set up.
Thanks for your attention.