Maybe if you buy OEM Yanmar. You can get a new 3GM johnson water pump for less than $200 from these guys http://www.depcopump.comTry $500. I had one let go the night before departure. No spare. Deck washdown pump plumbed right in and I ran some wire. Ran 14 hours straight. No problems. Why not have electric impeller pumps?What does a raw water pump cost? Couple hundred bucks? Sounds to me like you've tried everything else likely, and cheap, leaving only the most expensive part.