Of course it would be best to flush and rinse the motor after each saltwater use....but lots of folks don't or can't and they get many years of reliable service from their outboards....the anti-corrosion primers, paints and coating on outboards are really very good. Areas of outboards that can give corrosion problems are the cooling passages and the threads of nuts, bolts and fasteners. If you pull the boat out of the water after every use then I'd say flush and rinse, but if your boat stays in the water then it's not so easy....unless you have a later model motor with a built in flush port...