Step 2: Pry the plate off. I use my Leatehrman knife blade for this and it works fine. There are many ways to get the plate off but what ever method you choose make certain it does not harm the gasket mating surfaces.
Be sure to CLOSE the engine intake seacock before prying off the plate or changing the impeller for obvious reasons. Some water will drain out of the hoses, after you pop the plate off, so a turkey baster, rags and or a sponge may be good to have on hand to dry everything up afterwards.