Thanks for the info - just the kind of detail that will save people a lot of hassle and money. I have a W58 but have just changed the pump and have an extra on in reserve (probably the same one you have).
Westerbeke parts are criminally priced. I had to buy a two-groove pulley for the alternator belts and it was more than $500. The single-pulley one was $80.
Finished the circumnavigation in early February in Grenada. Have to work on a book project for the next several months so the boat will be waiting for next year.