I show how to take the lower footer off and replace the impeller on my Yamaha 2-stroke C90TLRX 90hp. The procedure is similar across Yamaha outboards including the 40hp, 60hp, 70hp, 125hp, 40 hp, 60 hp, 70 hp, 125 hp. The Yamaha impeller has a Tell tell that should be passing water in a visible way. Water pump replacement. For my 90hp Yamaha impeller rebuild, here is the kit, OEM Yamaha Outboard Water Pump Repair Kit 692-W0078-02-00. Tools you'll need:
12mm socket
14mm socket
Flat head screwdriver
Silicon based grease
Yamaha Impeller kit

Water pump and impeller designs for Yamaha are similar to Mercury, Johnson, Honda, and a few others. Hopefully, even if you don't have my exact motor, you can find some helpful tips in this do it yourself video. 2-stroke and 4-stroke designs are similar but are likely different parts.