From experience I can tell you that if it stuck due to rust you might want to replace it for peace of mind. There is nothing as exciting as coming into a dock
expecting to applying the brakes by reversing it and having the cable break. I had a similar problem some years back. Luckily I had a friend with me who climbed down into a very uncomfortable position to become the shift on demand person. Even then it was very dicey getting back to the dock
. The feel just wasn't there. I was lucky in tha the cable broke when I was in a cove a long ways from the dock.