has anyone replaced our speed paddle wheels, which keep getting mucked up
You don't say where you are. Mucked up could be a lot of things. Here in Lake Erie the problem is zebra muscles. I use VC17 bottom paint a very thin paint, I thin it down even more and put a very thin coating on the paddle wheel (removed from boat and transducer). Works most years. Some years it quits late in the season, then I remove the transducer, in the water, and clean it up. It's not as scary as it sounds. When the transducer is pulled out there is a rubber flapper that keeps most of the water out. I put a dummy transducer, a plug really, in for the few minutes it takes to clean the paddle wheel. Get maybe a cup of water in the boat.
Don't know if you have the same set-up or if you still have the OEM plug.
That's what I do. Not a recommendation to pull a transducer that hasn't been pulled for a long time while the boat is in the water.
Jim