Yup- been there, done that. I had a similar problem with a Chrysler Mitsubishi diesel on my Bayliner 3870; the parts supplier (Blue Ridge Diesel) told me he could get the pumps for $1500 each, or recons at $750 each.
Found a place in Oregon that rebuilt the pump perfectly for $110 shipped.
Water Pump Man
Give him a call- iirc, his name is Tony.