I am using a little L298 motor driver in an RC boat project. The problem is, I only have a small single cell (3.7v) LiPo that is capable of running the current-hungry motor. But the l298 doesn't seem to operate at that low voltage. Can I use a regulated 5V from a 9V battery to provide the L298 logic supply voltage (and all the electronics) while running the motor at 3.7V?

 

That's unlikely to work. The minimum voltage drop for the output of the L298 is specified at 1.8V at 1A, so that's going to leave you less than 2V for the motor. To work at such voltages you need a MOSFET h-bridge.