Current (I) Draw as related to thrust on Electric trollers

Hello,

New to this Forum, and happy to find it!!
I am in the market for a decent trolling motor, and hopefully with your help I will be able to choose more effectivly!

Now here is my question,

Does anyone know of a formula that can applied to find the current draw of a trolling motor at a givin thrust and Voltage.

I have the opportunity to use Aircraft batteries (24V or 12V NiCads), and want to figure out how big of a battery I should aquire, I want to avoid carting up a 95 pound Turbine starting battery if I can!!!


Also between 12 and 24V selectable motors, do you notice a differance in maximum thrust or just number of hours.

Thanks!