prop cavitation

[isabel98]

after changing all the drive components on my mark1, (except trans.) everything seems to work well. MY question pertains to a change in the "feel" of the prop (15x10 2 blade FOF)  under power. She drives the boat beautifully, but I'm getting about a 2-3 second change in the sound of the prop through the water. It almost sounds like a slight cavitation . I seem to remember my last boat ( a 30 Irwin) did  the same thing. I worked very hard on shaft alignment, and I don't notice it at low RPM. I think this change in "pitch" under power may be normal as the prop is spinning it might cavitate slightly and then hook up again. Any way that's what I'm hoping. I have very little vibration and the whole setup is new from the flange back. The condition is like clockwork and not intermittent. I hope I described the condition well enough, it could also be describe as a vibration, but it is not a steady vibration. I don't want to have to get involved with more alignment work, but I still have the wrenches ready if necessary. Thanks in advance for any thoughts on this condition.