[PSUBS-MAILIST] Does size really matter?

[Rob Innes <innespace@jett.net>]

I just bought a Motorguide 107# 36V trolling motor that I want to use to power
a DPV. One supposed expert told me if I discard the circuit board and run power
directly to the motor I could get much the same amount of thrust using only 24V
as long as I had enough amperage out of the batteries. Another , so called,
expert tried to tell me that the amperage or (Ah) was only important for
running time and to run as much Voltage as the motor could take. As I'd only be
under water for short durations, I'm not so concerned with how long the
batteries run for, as much as I am concerned with reducing battery size and
weight. My question is, Can I maintain maximum thrust by using smaller output
batteries, i.e. hooking up 3 small 12V 40 Ah batteries in series. A technician
from motorguide said I should run batteries of at least 200 Ah. Which battery
rating is most important for maximizing power output or is 36 volts the same,
regardless of battery size. Any well informed advice greatly appreciated

Rob