Arg, mine is in the engine compartment and easily accessed, but you didn't really want to hear that. LOL. Take a look at the specs on the existing pump. Then go down to any chandlery and get a replacement. As long as the input and output fittings are the same, it's a 12V pump Pressure Pump (meaning it has an internal pressure switch) and runs at relatively the same PSI and volume, then you should be fine. Jabsco and Shurflo are probably the most common. I suspect it's probably a Jabsco or a Shurflo you have in there now. Can't help on the removal tips/tricks though. Sorry.
Take a look at these:
http://www.defender.com/fresh-water-pumps.jsp
Notice it lists the Flow Rate in GPM (Galons Per Minute), the Water PRessure in PSI, and the Outlet size. You should be able to pull these specs off of the existing pump and simply find a suitable replacement. Whether you chosse JAbsco or Shurflo is completely up to you. It might make it a bit easier to find a direct replacement IF the screw pattern in the feet are the same size.
Make sure to install, or upgrade the rubber shock absorbers under the pump to reduce pump noise in the boat. While you at it, check the condition of the 12v connectors. If there is any corrosion replace those while you're in there.
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