Just before we left to go sailing on Moreton Bay, I rebuilt the raw (sea) water pump with spare parts I had bought in San Francisco, some 2-1/2 years ago. New bearings, a lip seal, a new impeller, etc.
If you take your old bearings and lip seal to a bearing supply house they can supply generic replacements for about 1/4 of the cost of Yanmar parts. Just make sure your lip seal has a s.s. spring or an O-ring. It's not hard work really to do the rebuild, once you realize the 2 bearings have a circlip between them and you have to seperate them to get them off the shaft.
And when you put the pump back togther - the pulley is not symmetric. It's dished on one side. If you put the pulley on with the wrong face facing the pump, the V-belt won't line up. At all. Though you can convince yourself that all is well if you're trying to go sailing for a long weekend. And motor for many hours with the pump working with a V-belt that is totally off by about 1 cm or more. When you put the pulley on the CORRECT way it looks much nicer.