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GA_Boater ?
There are two O rings inside the black plastic seal carrier (#29) that sets on top of the water pump outlet. One seals the pump housing outlet, the other seals the copper supply tube. The white tube (#31) sets inside the top of the seal carrier. It doesn't do much, except help you guide the copper supply tube into position at reassembly. The tube seals tight in the top O ring of the carrier.
I clean up the lower O ring and pump outlet and use 'Perfect Seal' (Permatex Aviation Gasket) to help hold the carrier in place, grease in the upper O ring and on the lower end of the copper tube. You can tack that white tube into place with a little AV Gasket.