Best way to keep barnacles of a unpainted hull is use the cheap out of it.
I bottom paint my boats only because they are in from May sometime till late December if stripers are running.
When you pull the boat after vacation hit a coin operated carwash on the way home and wash it off good.
You will most likely get grass growth on the waterline then barnacles.
If you feel the boat is slower then you might be getting a build_up.
Good luck and enjoy your vacation.