The mercury socket and the shaft securing tool are really slick, and in my opinion worth the money - the socket can be fitted to your impact wrench which will help with the removal and it has a smooth hole to slide over the exposed shaft to avoid nicks and scratches. The shaft wrench fits snugly over the shaft and uses the sides of the intake tunnel to prevent the shaft from turning - works like a charm.
You can purchase a 1-13/16 inch standard socket and piece of 1-1/2 inch black iron pipe. cut the socket in half and braze the two socket pieces to the pipe and then you can remove your impellor. I had the local machine shop do it. The total was about $60.00. I removed the grate and used a small pipe wrench to hold the shaft.