Lets look at some facts:
1) The breaker is tripping. Breakers are safety devices. The goal is to not have a fire. Hmmm, wonder if anything is going on? Let's check!
2) Wires are getting hot. Hmmm, that's not supposed to happen, is it???? Is something wrong? ....something going on that shouldn't be?
Maybe the breaker is trying to tell me something? Nawww, I'll just increase the amperage so I can allow a meltdown to occur, maybe burn my boat!
The heated wiring is due to over-amperage. Over-amperage can be caused by one of several faults or a combination of them. All of these faults are circumstances that introduce added resistance in the wiring and connections, or maybe even the motor armature's windings. Added resistance causes a voltage drop, and it takes more amps at a lower voltage to get the same watts of power.
Check that ALL wiring and connections (positive and negative) for the batteries to TM and back are clean, tight, and free of corrosion. Chalky green or white corrosion on terminals or wire strands is a no-no. This can even grow into the wiring underneath the insulation. Such wiring needs to be replaced. Any connection that isn't snug will introduce voltage drop, and could be a cause for an increase in current flow that's heating the wire and tripping the breaker.
A battery nearing failure can provide less voltage. This could cause the TM to draw an unintended increase in amperage in attempts to generate the same thrust that was once delivered without the extra amps. Check each cell of both TM batteries carefully using a good hydrometer (inexpensive, available at auto parts stores. Don't use the cheapie pocket hydrometers with floating balls)
An 82# Minn Kota should never need more than 50 amps. Upsizing a breaker is NEVER a correct solution if the breaker was properly sized to begin with. Breaker trips are intended to bring a problem to the user's attention.
If wiring is in good condition, and batteries check out, you could replace the breaker with another 50A breaker to see if the breaker was causing the problem, but I doubt that. If you rule out wiring and batteries, the cause is usually a short developing in the armature of the motor, causing it to draw way more amps than it should. There are tests for shorts in motor armatures if you have a meter and know how to use it.