With trailer boats, I usually use a on-off-on switch to control the auto and manual modes. When in the water, I set switch to auto which allows it to operate off the float as needed. Manual will run it whenever I want. Off allows it to be totally disconnected if I'm on the trailer and don't want it to cycle automatically.
This does require a fused hit lead directly from the battery to use as a supply for the pump as most of the power for the panel will be connected to a battery switch (which you turn off when not using the boat).
I also stick with the old school pumps with float switches. Some newer pumps have 'sensors' which cycle periodically to check for water and will drain battery over time.