I'm in a similar situation. I live on a saltwater bay off the Gulf, but the freshwater ski lake is 15 miles away, 25 minute drive to the ramp. But, my current Mastercraft hasn't touched saltwater since I've owned it. I have an outboard skiff that I use on the Bay and Gulf. If I want to ski, I hook up the MC and tow it to the lake. In fact, I use the MC on the lake a lot more than the skiff on the Bay, even though the Bay is right outside my back door.
I had an older Prostar that I took out on the saltwater a few times. No apparent ill effects on the boat - I thoroughly flushed the engine and rinsed the boat - but the saltwater really ate the trailer up bad.
Another issue is that those small MC boats like yours don't do well in rough water which you will likely encounter on the Bay, especially on weekends with heavy boat traffic. At least that's the case on our Bay.
2003 Prostar 197 35th Anniversary
1990 Prostar 190