Freshwater flushing is a very good idea. It will help keep your raw water cooling side cleaner, less corrosive, and allow you to go longer between full servicing of the raw water side.
I am not a fan of "descaling" (ie. using products like Barnacle Buster) as a substitute for proper and complete "off engine" servicing of the various raw water components, while others here will disagree (which is fair).
Descaling should only be a temporary "clearing' of the small passages to allow for the completion of this season, so that full servicing can happen in the fall/winter (after noticing a temp rise).
Full servicing includes: removal from the engine, full cleaning using acid, ultrasonics, rodding,etc., replacement of O rings and/or gaskets, a full pressure test to ensure no internal leaks, and reassembly (possibly replacing hoses and/or clamps as needed). Also flushing (if needed) the coolant side and changing the coolant.
Full servicing will ensure that all impeller pieces, pieces of zinc, deposits, and sea creatures are removed. It will restore the "component" to "like new" condition (new gaskets etc.), and will ensure no leaks. You don't want salt water in your oil, coolant, transmission, air intake, etc. Using products like BB will only help clear away calcification, and not accomplish all of this!
Engine overheats can severely damage the engine. Internal leaks can cause extensive damage as well. Preventative maintenance is needed to improve your chances of avoiding costly damage and the associated "headaches". JMHO.
For more on freshwater flushing, see sbmar.com under "Tony's Tips" and look it up in the forums.