Sorry ,after a re-read I saw you were doing the water pump. It's a very simple job. When you are removing the bolts holding it on , there is one hiding under the skeg fin. Wiggle the assembly down until the shaft clears. I hold mine in a old workmate table. The 4 or 5 screws come out and the cover comes up. Watch the seal ,don't scar it. The impeller has a key. re-install with the impeller twisted like the old one came out.
I've seen a couple really worn out ones and some that looked good ,replace it anyway.