I was under the impression that salt crystals are not the problem (this and the other flushing thread), since they'll wash out or dissolve the next time anyway (unless you are in saturated salt water), but flushing is for corrosion protection. Leaving saltwater in the aluminum engine encourages it to dissolve into a pile of aluminium oxide. The crystals referred to, I suspect, are alumium oxide (al203 I think), not salt, and that's why they don't dissolve, I failed chemistry a-level, but I do seem to remember aluminium oxide being particularly insoluble.
Engines these days do seem to be much better at resisting corrosion than years ago, but always flushing with fresh water is just good practice. Hopefully this engine has an external flushing connection as many of them seem to these days.
Either way, make sure all your anodes are, and remain, in good condition, and raise the engine clear of the water when not in use.