I used to do the same thing as Bill (in the same lakes too!), nay a problem. After riding I'd do a quick winterize at the launch too (pull the drain plugs, blow the water out of the heater core, make sure the water is out of the shower...).
In my old boat, the impeller housing was pretty low in the engine area and the intake open to the stranier. So, I'm not sure there was much difference in the amount of water in the impeller housing between a drained block and not, once the boat is in the water for a few seconds before starting.