Impeller located on 1966 mercury 3.9 hp outboard motor?

The impeller is located in the lower section of the motor near the prop. Take the two nuts off and the lower unit will separate from the top. Remove the O ring and the seal from the long shaft before removing the two nuts from the water pump housing. Good luck removing the impeller itself. I had to cut the soft brass ring with an oscillating tool. A paint can opener also helped in the removal.