Flush that motor!
The very best thing you can do for your engine after running it in saltwater is to FLUSH IT OUT! I know at the end of a day of fishing and perhaps fighting some really tough fish the last thing you want to do is to take care of your outboard motor. If you keep in mind that outboard motor kept you on the water all day long and turned a Saturday into a day to be remembered then the one thing you should take the time to do is to flush your motor with clean fresh water.
Flushing is not only running the engine on a garden hose, it is also pulling the cover off and rinsing the engine. Don’t worry if you keep it out of the intake (where the motor brings in air) you can’t really go wrong. Also pulling the engine cover each time will help you to spot areas where corrosion is just beginning. Clean those areas especially well and liberally spray your engine down with a quality silicone spray. Doing this and flushing your engine with muffs and a garden hose after each use in saltwater will prolong your engine’s life and prevent possible running problems caused from corrosion from occurring.
Here is a link to a page that goes into more detail and can answer many of your questions and a video of corrosion in an outboard motor.
Here is the link to more information about corrosion.