The technology of outboard motors came along course. Small outboard motors are truly self-contained. They'll have integral fuel tanks and control linked to the body of the motor and steered with industrial 500kw diesel generator generator tiller and connected into the motor. Small motors can weigh as young as twelve kilograms and supply sufficient power to move the boat close by. They are portable and capable of being removed by loosening the mounted clamps.
Backup systems are meant for Off-Grid not really. By definition you do donrrrt you have the Power Company's power. Your stored energy is your first line of backup. Which needs to be designed for the 24-hour stream. What do you do later? If your solar, wind and magnetic power sources no longer work you'll need a gas or 75kw diesel Generator generator. Because you might have energy storage, you only have to recharge the batteries and that will take a way smaller power generators.