I'm sure A FEW guys will be put off, but probably not as many as you fear.
Scars wouldn't put me off. If I saw them, I'd feel sorry for the girl and ask her what had happened. I'd make sure to put in extra effort to make her feel good about her body.
Guys do care about visuals, true, but it's more "Does she have big boobs?", "Does she have a nice butt?", "Does she have a pretty face?", rather than "Is her body perfectly free of scars, stretch-marks, etc?"
I'm guessing these scars are on your chest area. I wouldn't even get to the position of seeing them unless I found the girl physically attractive anyway.