Yamaha Salt Water Series versus not stated

[Pacific Lots]

I have a newly purchased 150hp 2004 yamaha carburated that is not specified as a "salt water series" motor. I live in Key West Florida and the closest fresh water is basically Lake Ocochobee, hundreds of miles from where I live. Was the designation "salt water series" just a marketing plan or is there a big difference between a motor that does not state Salt Water and one that does. Should I plan to sell the boat now to someone on a lake or am I good to go in the ocean? My boat sits on a mooring for 3 months a year... Answers Please...