I have a three bladed Kipawa propeller for my trolling motor and it's started to show strong vibrations. (Definitely not the "good vibrations"). Vibrations are strong enough that the shaft will not stay locked and the motor starts pointing sideways... makes me think that whatever the impalance is, it's not a simple question of weight imbalance - nylon isn't very heavy to begin with.
Also, no vibrations can be felt when the propeller runs in air.
Anybody ever have the same/similar problem and is there a remedy other than sending it back in?