I have owned several (and do now own) Suzuki 140's. They are a much weaker motor than then Suzuki 150 (which I have also owned). They are the 115. block, and then with valve timing changes, and more air/fuel induction get a bit more HP than the 115.
I don't believe that you will be fully happy with the performance on the Tom Cat. There have been several Tom Cats with both the 115 and 140 Suzuki--just don't have the speed. If you kept the boat very light, then you can get decent performance.