I have never once boated on Fresh Water. Salt water is nothing to be scared of from a boating standpoint unless you don't use precaution, or don't flush like you should.
I echo everyone else's recommendations. I normally flush with just water for about 2 minutes BEFORE firing up the engines (to get the drives good). Then I fire the engines up and flush for a couple minutes (no thermostats here). Then I use salt away - buy the adapter kit at Boaters world - until it ocmes out of the pipes. If you have a switchable exhaust I also make sure I run salt away through taht at some point.
Salt Away is a great product - I bath in it, and even garnish my drinks with the stuff. Feel free to coat the outdrives, tabs, steering rams, and TRAILER with it top to bottom leaving a nice film until you dunk it back in the fresh water. It may not look shiny on the way home, but it will be well protected.