Where I sail is a nature preserve and no gas engines are allowed. On my Elan 19 I have a 550W Minkota E55. This is the most powerful 12V trolling Minkota there is but it's still only about 2/3 of a HP.
I flat water I can get 2.5 knots but it will not punch into more than a force 3 headwind. I only use it to get back if becalmed. There are boats with several kW electric motors but these are hugely expensive.
Unless you are on a lake or very sheltered waters with never any current, forget it. Buy a gas O/B.