Can I clamp the electric motor directly to the crossbar?

I am a newbie and not quite handy and in the market for a Getaway. If I find one, I will definitely add an electric motor to it. If I use a mount, it will involve drilling holes in the crossbar. I was thinking, why can't I just clamp the motor directly to the crossbar?
I was thinking I can throttle until I reach open water, then unclamp and remove the motor, tuck it in the hull, then hoist the sails. On the way back I do the reverse. Is that doable?