0E010603 is your serial number, not the model number. This is fine because the serial number is the number you need to order parts. The following link will take you to a parts book for your engine - click here - select which section of the engine you want to look at, "gear housing" for the water pump.
Marine Mechanic
11 years experience working on outboards, inboards, sterndrives & pwcs
Not a problem, for future reference www.sierramarine.com has a pretty good parts interchange to their part numbers. Just click on "parts interchange" in the center of the page and enter the OEM part number you are looking for. If they have an equivalent it will come up. If you have problems finding Sierra parts locally you can also try GLM (www.glmmarine.com) or Mallory (www.mallorymarine.com)