Upvote:1
Ferries in Europe are generally pretty reliable, however you aren't giving yourself much room for error.
If you can take the ferry a day earlier, you would save yourself a lot of stress by not having to worry about making such a narrow window. But they usually depart/arrive on time, so you probably wouldn't have an issue.
I found a forum about Croatian ferries at: http://www.croatiaferries.com/forum/index.php you might get a better (or more specific) response there.