DC-DC step up converter for electric vehicle project

Can I use a 12V deep cycle marine battery to power a 90V/6A DC motor by constructing a simple step up converter? How would I go about building such a converter?

Thanks!

It's suck 45A min. from 12V! With simple step-up converter no possible.

Your vehicle would run only a few minutes from one deep cycle marine battery with its voltage stepped up.
Usually one would use 8 batteries in series to raise the battery terminal voltage to match that of the motor. This way only 6 Amps of current is drawn and your battery bank should cope for a few hours with that.
Now, 8 big deep cycle batteries take a fair amount of room and weigh as much as two adults - that's why so few electric vehicles are seen on the road.

There's no magic with voltage converters - only losses :?
Klaus