View of the assembly with the 4 bolts of the casing removed, and opened up.
Close up of the cast brass marine circulating impeller. This is a sand cast piece of brass, and it's not cleaned up at all, and it shows virtually NO WEAR because this one was used in a closed cooling system. Had this pump been pushing river water with silt, I would expect to see all the silica held in suspension in the water having taken some sort of a toll on this brass.
Here is what the other end of the pump looks like.
Hope this helps in the understanding of how these work, and assists in the ordering of new impellers, gaskets, etc. You can always send a link to the shop and let them look at these photos to be sure you are talking about the same pump.
Regards,
Paul