Ayuh,.....
Then I guess the 1st thing to do is Pull the Seawater Pump....
Once you get it Apart, You'll know whether it needs a Rebuild, or Replacement....
Btw,.....
Welcome Aboard to the forums here at iboats.......
I'm not sure I understand that statement. I would think it would make sense the other way around -- The belt is not moving so the pump is not turning. The belt turns the pump, not the other way around.
This is a serpentine belt, correct? Is the belt tensioner too loose perhaps?
What you need to do is remove the belt, then try to turn each pulley and see which one won't turn. The sea water pump may be the problem, but when you try to turn it, don't forget that it has a rubber impeller and will be harder to turn than any of the others. All the others (Except the crankshaft which is what makes the belt move) will turn very easily and freely. If they have rough bearings, they could lock up with tension on them.
