The shaft "sealing washer" (as Volvo calls it) is actually a lip seal. Just like the oil seals used on the Amel propshaft, or an engine crankshaft, or any number of other places. In most applications they last at least as long as a carbon face mechanical seals. It is listed as an "obsolete" part because Volvo does not stock it any longer in their part supply chain. It is a standard industrial part, although a bit hard to find because of the stainless steel garter spring.
The raw water pumps, and raw water pump parts, for the D3 were (and still are) made by JMP and are readily available at a fraction of the price than from Volvo. If you know the Volvo part number for your pump, you can cross reference them and get a new pump or any of the parts if you want to rebuild them yourself. My understanding is that there were at least different two versions of the pump used on the D3 engines. A complete new pump is less than US$400.
Same with the TMD22: Those raw water pumps are made by Jabsco. Look closely at the cover plate, and the Jabsco number is stamped there. Dealing with a Jabsco distributer will save you a boat load of money compared to Volvo.
At least some of the Onan models used Oberdorfer pumps, again these are usually clearly stamped with the original maker and model number on the cover plate.
I'd give very long odds that the Yanmar raw water pumps are also third party supplied, but I do not know which supplier Yanmar used.
Charleston, SC, USA