I don’t think Gunboat can take Johnson but 1914 is about right to give him a chance. As @JWSoats mentioned, Smith has a win over Langford around this time, is on a pretty good run and Johnson is far from active. Maybe if Jack has enough rust Smith is able to make a good go of it, but over the course of a fight you have to figure Johnson takes control at some point.
I’m going to link directly to Hellers book (includes the chapter on Gunboat), free read (borrow) on Internet Archive. It’s a seriously easy, no strings attached sign up, just provide and create you email, password respectively - takes less than 5 minutes - and there are many more boxing books and mags to look at. There is also a ton of the old Police Gazettes going way back. Just click the head bust icon in the top right corner to register. https://archive.org/details/inthiscornerfort0000hell