Closed cooling system??

[Dixielegger]

Found a '97 SN with a closed cooling system for sale. I know very little about this as most boats in the south have fresh water cooling. What's the advantage/disadvantage? Boat was used in brackish water. Is there still freshwater taken in somehow (exhausts)? What effect would brackish water have on an engine with closed cooling? Any info would be helpful.

Dixielegger
'80 Nautique