I am trying to install a used TM. I installed a new plug on the TM wires and noticed this bundle of wires that ran along the wires for a short distance and then were cut off (so not attached to anything). Do these power a sonar unit? I am hoping they are not necessary for running or controlling the motor

Looks like it would be for a sonar unit. Trolling motor wires SHOULD (heavy emphasis on should) be heavier gauge. 

this bundle is really light gauge and the two TM wires are definitely heavier gauge.

So neither end of the wire is attached to anything or has any type of plug attached?

What make/model is that TM - that would help narrow down the options.

its an old maxuum. One end of the wire attaches under the foot pedal but the end shown in the pic was attached to nothing

I'll take a wild guess.   

 

Looks like there is a control board upgrade available that includes several wires.  Maybe it was installed on this motor and the wire in question was left after the upgrade.   If the trolling motor doesn't work after you install it then you probably need to find out what to connect the wire to.

 

Good luck.

 

https://northlandmarine.com/products/24-36-volt-control-board-2884052

Lemme know if you need some maxxum parts