Re: How to fresh water flush on Mercury 9.9
During the season, when it gets frequent use, I don't bother with fresh water flushing my 2 stroke Merc at all. You don't see professional fishermen bothering to do this, and in third world countries they probably never do it either. Yet these little two strokes go for a very long time.
At the end of the season my outboard gets a special treat in a very large bucket of fresh water, being topped up by hose as necessary. A good 10 minute run at about half throttle (in neutral gear, of course!).
Then I run the carb dry, change the lower leg oil, pull the spark plug, spread a bit of inhibitor spray around inside and outside, replace spark plug and put it to bed. During the winter I pull it over on the starter occasionally. Come next season it fires up first go. Motor is now 5 years old and still looks new.