Dual extruder setup in Marlin I have a Tevo Tarantula with a MKS Base 1.5 board and dual extruders.  I am running Marlin RC8 Tevo Community build for the dual extruder, large bed and SN04 sensor.  

All temperature sensors work and give accurate reading but E1 when activated runs at 100% until the overtemps kicks in and shuts down the system.  Like I said, it reads proper temperatures through the thermistor it just won’t stop at the set temperature.  I checked the MOSFET and there is no obvious scorching or bad solder joints on the MKS board.  This leads me to believe it is a mix-up in firmware but, being a bit of a newbie on this, I am still getting familiar with G-code and Marlin.

I have confirmed the correct board is being referenced in firmware from boards.h but looking at configuration.h I just get confused.  What I am thinking is somehow/somewhere E1 might be referenced as a fan that is just off or on.  Anybody have ideas?
I am not sure what the hardware config is for the Tevo Tarantula

Make sure your configuration.h file is setup for your hardware.
The extruder defines are describe in Conditional_LCD.h

It looks like the configuration.h file on GitHub is configured for a single extruder.

For example, if you have 2 hotends; but, "HOTENDS=2" is not set then the I/O will not be configured for the 2nd hotend.  I just looked at the code and if HOTENDS == 1 then the MOSFET_D_PIN will be used to control FAN1 (which sounds very similar to what you are describing that you are seeing).

  #if HOTENDS == 1
    #define FAN1_PIN     MOSFET_D_PIN
  #else
    #define HEATER_1_PIN MOSFET_D_PIN
  #endif