The sleeve goes over the shaft and this all inserts to the tail housing. Running the slity/salty waters we do in Ak requires good maintenance and don't be afaraid to put the grease to it often
Here is a link to some good pics and info. The sleeve is the 3rd picture.
Great link Dupont
So the impeller shaft runs in the cutlass bearing. What is the housing that touches the outside edges of the impeller tips ? The edges that get dinged by rocks and stuff? I have noticed that the tube that my impeller edges run up against is a bit scratched up and I can see where at some time in the past the jet ran up against it and scratched it or it was a rock that was sucked in and went around a bit. Is this surface important?
The tube around the impeller is the impeller sleeve. The impeller sleeve is very important. The impeller runs in close tolerance to the sleeve to help push water out under pressure. As the gap between the impeller and sleeve widens you lose efficiency. The vanes (stator) you see are to keep the water from spinning (loss of efficiency) on exit.
It's also important to never run your jet without water. The impeller can contact the sleeve and very possible to ruin your shaft bearings.