Hi not sure if you have the plastic gear or the brass
I have had both, be careful what grease you put into the plastic ones (they don't last long with grease) as they are water lubed and cooled.
If you have the large size then you will notice a thru hole in the forward facing cone, pass a strong small steel bar through this and unscrew the cone slightly. Remove the small cir-clip that holds the Kort blade prop onto the shaft and pull the prop off (it is located on flats on the shaft) then remove the cone completely you can now draw out the lower shaft.
To remove the down shaft you have to remove the top sprocket (drive wheel) this is also held by a cir-clip, pull this off and you will fins a short steel pin through the down shaft, slide this out and keep safe, the top bush needs to be drawn out of the body to allow the down shaft to be removed.
The whole unit will drop out of the hull fixing boss once the top drive sprocket / pin and the steering sprocket (square center) are removed.
I found that if these units are filled with chain lube then they are much quieter and last longer (for me the did)