I had to stop my boat this weekend, drop anchor, and dive under to chisel off the barnacles from my prop.
It's the right time of the summer for it. Same thing happened last year at this time.
The barnacles will seriously load an engine. And you end up throwing water out the sides of the prop instead of out the back.
ps. use gloves! Get a mask, and I used an 18 inch prybar as my chisel. Tied it with rope to the boat so it wouldn't get lost.