When my outboard stopped pumping water, I knew the impeller was shot. I was nervous about tackling the job myself, but it turned out easier than I thought.
I dropped the lower unit, swapped in a new impeller, greased everything, and bolted it back together. The whole job took about an hour with basic tools.
Now I replace it every couple of seasons for peace of mind. Overheating an engine is way more expensive than a $30 impeller kit.