My Evinrude could be flushed using freshwater hose and hoods whilst tilted up. The marina was ok about it but some of the occupiers got a bit snotty if it went on for long!
On my Suzuki there is a Screw out plastic bung that you can attach a hosepipe to, I keep my rib in a marina and tend to just connect a hosepipe to this and flush out the leg when the engine is tipped up out of the water.
You can flush many outboards by hosepipe attachment (threaded port on the engine, not muffs) with the leg either down or tilted, but never run the engine whilst it's tilted up - you are risking water running back into the exhaust port. This is particularly dangerous for 2-strokes.