OK, you are not getting much traction here so you will have to do your own detective work. Fortunately its not hard, especially as you obviously have internet
I am assuming we are discussing the raw water pump
First thing to know is that Yanmar don't make their own pumps, they buy them from the major pump manufacturers. If your engine serial
number begins with the letter E, chances are the pump is a Johnson. If you can determine the make of your pump, it is even easier. IME, Yanmar just paint
over the manufacturers name and model number when they paint
the engine at the end of assembly. Have a very close look at your pump cover and see if there is a manufacturer and model number stamped into the metal and then painted over with Yanmar grey. With this information, the part number of the parts should be easy to find on the web.
If you can't determine the make and model, never mind, it just means a bit more investigative work needs to be done.
First the impeller, have a very close look on the face of the old impeller near the hub, you may still see the part number moulded in the rubber. If not, then you will have to measure the old impeller and search the web for a SPX impeller catalogue. The important dimensions are the overall diameter of the vanes, the number of vanes, the width of the impeller, the hub size and type.
Next is the seal, again, once removed and cleaned up, you should find its part number moulded on the larger face. I have never seen one that is unreadable but if you can't read it, measure it. The important sizes are the OD, the shaft diameter and the width. Also remember this is salt
water seal, not a oil seal
although the right size oil seal
can be used in a pinch. Simply remove the spring steel
garter spring from the inner part of the seal and replace with a suitable rubber o ring. Again an on line catalogue from seal manufacturers with be your friend.
Now for the bearings. You normally don't have to replace the bearing very often, they should last thousands of hours, not hundreds. However if sea water has got to them, you may need to replace them. You can tell by feel. If there is any slop in them or they feel gritty when rotated or noisy, you need new ones. Once again, the part numbers are often visible on either the inner race
face or the outer race
face. Clean and look carefully. Of course, they can be measured just like the seal. OD, ID and width is all that is required. Remember these are just general pupose ball bearings, nothing fancy. Try the big manufacturers on line, SKF or NTN or NSK or Timken etc.
To recap, your raw water pump
will be made by a major pump manufacturer, the impeller, seals and bearing are all made by major manufacturers and sold to the pump manufacturer.
The part numbers are often still readable on each component but if not, they can measured.
Pumps made in Europe
will usually be metric while North American pumps are usually imperial measurements.
Good luck, it's not hard if you still have the old parts.