The Merc 6 HP I had didn't use the ear muff style flushing attatchment. I had to get one that slid onto the antiventilation plate and had a single
plunger looking thing. Of course you have to remove the prop to do that.
You should not run it out of water
, including starting it then tipping it up. No water flow is an unhappy condition for the impeller.
I can't imagine how doing this would have gotten water into the engine