[pirateofcapeann]

Part of my Mr. Fix-It business is to get a bit more use from older stuff so my customers have the time look for the best deals for new things. This includes older outboard motors. I have a 55-gallon drum filled with fresh water to test run and flush motors with. I''ve had to remove the heads from older motors that were stored, unflushed for the winter, to remove the aluminum oxidation "salts" from the water jackets. It’s rare that I run into a motor where the corrosion has degraded the aluminum castings to the point where they are no longer usable. But it does happen.

Now, I really doubt that you need to freshwater flush the motor after each use in seawater. I would recommend it if you plan to let the motor go unused for a period of time, say greater then a month or so. I would also recommend that you run it up in seawater once say, every other week for 15 minutes or so to heat it up and flush the old seawater and oxidation out.