Thanks Charlie and root,

The whole Idea is to use a lighter cable on the run from a single
battery to the engine, to save weight and expense of heavier cable. A
24V starter should also turn the engine over more robustly. The idea
is to not have a complicated system of two 12V batteries in series and
still only run 12V all that way. A typical 24V starter uses about 100
amps and a 12V starter uses about 200 amps. So using safe wire sizing
for those amperages and total 40 ft. run, thats the difference between
#2 wire and 3-0 wire. A difference of about 15 lb. Regarding one
other idea, I would be leary of down sizing the battery cable to the
point of getting even a 10 volt drop over the run at risk of over
heating the wire.

Larry