Need help on 12/24 volt troll motor

[BassBandit]

The motor is Motorguide Brute 756 with 12/OFF/24 switch on foot control. The male plug is 3 wires black, red and white...four 6-gauge wires hooked up to female end (red, black, red w/blue stripes, black w/blue stripes) the wires goes all the way to the back hooked up to 2 deep cycle batteries.

When I put red and black to battery 1 & red/blue and black/blue to battery 2, it runs on 12v when the switch was set to 24V mode. Flip the switch to 12V mode, doesn't work.

So, I tried other way, red on pos. post on battery 1 and black on neg. post on battery 2...leaving the blue stripes wires untouched..using 6 gauge jumper from neg. battery 1 to pos. battery 2, with the meter on pos. and neg. it reads above 24V while the mode is set on 24V but does not spin the prop?

I bought the boat last summer and the whole time I've been using the TM on the lake I thought it was running on 24V but it was on 12V even the mode was on 24

Called the marina today and they said it will cost me 45 for half hour to 90 for an hour to correct the problem. Can't afford it.