I don't know how many amps a trolling motor draws but they do make DC/DC
This page http://www.powerstream.com/dcdc.htm has some listed.
Here's something similar from Surplus Center:
On 07/26/2010 01:28 PM, Matt wrote:
> I shoulda just gave the whole story up front. I cart off timed out 24V
> batteries from work (they were paying to dispose of them!) They still have
> good life in them and I was going to use it to power my canoe on early morning
> fishing jaunts. They make 24V trolling motors, but I was looking to just get
> a cheap used one and you rarely find the 24V used - plus they are usually much
> higher power motors.
> Some airplanes have a "cold start" switch that will put your typically
> paralleled batteries in series for a little extra electromotive umph when very
> cold. I guess the starters are engineered to accept this higher voltage
> without serious problems given the limited times that would be used.
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