Going from a 12/24v to 24v which is better to do? Tape off and do not use two of the wires or double up and use 2 pos and 2 neg wires running from trolling motor plug to batteries?

You need to find out what gauge wire you have right now and what gauge your trolling motor requires for the distance of wire. I had 8ga wire and removed one. The TM would not run more than a minute or so on high before it would overheat. I just removed all the old wiring and replaced with 6ga and problem solved. If you did use both wires in combination, you have to rewire it on the battery side so that they both were 24v.

Almost all TMs will require #6 wire and all of them will run better with it because of less voltage drop. No one ever got in trouble using wire that was too big.

If that is your boat in the pic, the Ranger will be wired with 6ga and have 4 wires going to the front. The 4 wires in the front represent each of the 4 battery studs (two batteries). The 24V jump in your case is made in the plug. there is no need to double wires, but you do have a couple of options. The first being leave it like it is and connect to the same terminals in the plug that is carrying the 24V not (will be the two that is not connected to the jumper strip). this gives you a 40' jumper and will cause a small (usually not enough to worry about) voltage drop. What it does do it makes you use and extra 60A breaker since both positives going to the front need protection. The other is to disconnect the positive on battery one and negative on battery two, then disconnect the same wire in the front. Wire the 24V into the remaining pair, then place a 6ga jumper from battery 1 positive to battery 2 neg with one breaker in the positive wire going to the front. Either way will work for you.
John

Ok here's how I understood to wire it for 24v. The pics are the plug, receptacle and batteries.

looks good, I'm assuming there is a breaker / cutoff switch on the positive wire

Here is a basic 12/24 wiring just abandon the 12v wire.

Yes, top right of the batteries in the pic, the wires go into a breaker.