Cavitation from Clogged Inlet?

[3littlepigs]

I took my 97 Speedster out on the river 2 days ago. The current on the river was fairly high because of all the rain we've had here lately. Plus there was a lot of floating debris.
After warming up the engines by running at <2000 rpms for about 10 minutes. I tried to go to full throttle. But the starboard side started to roar and vibrate as soon as it hit above 5000 rpms. I ran the boat for about an hour but every time I ran the starboard side above 5000 rpms it would happen.
I then anchored for about 45 minute. After which I wanted to test it out once more before calling it quits for the day. I slowly increased the rpms on both engines but this time I was able to get both up to 6500 rpms without an problems at all. I did this several times again without issue.
Was my issue as simple as a clogged starboard intake? And then being cleared at anchor by the fast moving water of the river?
Thanks.

 

[racerxxx]

It can take a small piece of river grass wrapped around an impeller and the pump will cavitate. You could literally shut the boat off and turn it right back on and it could fall off and your good to go.

 

[3littlepigs]

Wow. I guess that makes sense. The grass spinning at high speed causing areas for cavitation to start. I guess I thought with the high speed of the impeller and high water flow that stuff would just get all blown through. But I guess that 99% of the time this is true. It's that 1% that causes grief.
Thanks

 

[3littlepigs]

One more question.
Is there any rule of thumb here. Like the more obstruction you have the lower rpms your cavitation will start to happen?
Thanks.