Replacing 225 water pump

Hi,

That "star wheel" is called the impeller and you would not remove it to put the gasket on. If you are referring to the pump in the picture it looks like there is a little rust on the pump face gasket surface, I would clean that up a little. I like nice, clean, smooth gasket surfaces so there are no leaks. I have always used Permatex #2 sealer for this type of thing. Position the gasket on the pump so all the holes line up then remove the gasket and use your finger to apply a thin film of Permatex #2 to the gasket side that was next to the pump face. Replace the gasket on the pump with the sealer side toward the pump. Now use your finger to apply another thin film of sealer to the side of the gasket that has none on it yet. Now mount the pump on the engine. I like to remove the radiator when removing or installing pumps to give me some working room. When replacing the mounting bolts put some sealer on the threads of any bolts that go through to the water jacket or pump cavity.
When you tighten the mounting bolts a little sealer should squeeze out from the gasket so you know you have a good seal.