danger zone... danger zone... which boss is that again? Is it BigBoy?
In any case, a high amount of HP is required... at least 1,000. Defeat the minions and enter the boss fight with a full HP.
If your mech is not very strong and takes damage from the minions, I hope you managed to get at least 3-4 repair kits.
Using a heater mech is suggested because BB has very low cooling. Though I use an energy mech and overpower it by draining the energy...
Yes, post a pic of your mech. You can get better recommendations that way.