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.