You know I was just kidding about the photography.
I'm not convinced that you have a problem, we don't have a problem with weeds, however earlier this year I thought I had a problem with cavitation, turned out it was a piece of a plastic ice bag wrapped around the drive shaft, it doesn't take much.
Here's something I learned from Dr Honda, I've never tried it by I will pass it along. Pull the rubber bellows back exposing the carbon ring. Apply a blob of waterproof grease on the carbon, it this temporarily fixes the problem you need a new carbon ring.
Lou