Disable M116

Hi there I´m new in to the 3D printing world, I made a core-xy 3D printer using an Arduino Uno with the Teacup firmware. and I´m currently using
Slic3r 1.3.0v to generate my g-codes, and Pronterface to run the g-code. All works perfect, the speed is good, the printing quality and accuracy are great. The only annoying thing is that when I hit start printing, the printer says "wait for temperature to be reached" and the current temperature gauge freezes, (ok that is normal I guess) but it does that even if I manually preheated the hotend (at 185c° for PLA) and then hit the print button. Then after few minutes of waiting, the print start, but the starting moment seems kind of random regardless to the temperature of the hotend. So what I have been doing is editing every g-code and manually deleting the code line "M116 ; wait for temperature to be reached" . That works just fine, but I would like that Slic3r do it automatically. I know that you can edit start and end g-codes in Slic3r (in Printer Settings / Custom g-code), but there was no M116 there, still when I export the g-code, the M116 is there. So I want to know if there is any way to edit that part of the start g-code in Slic3r and get rid of the M116 entirely.
I know that I will have to wait for the temp to be reached and then manually start the print, and I´m ok with that.
P.D. I also had some clogging due to heat creep because of the 3D printer just siting there "waiting for temperature to be reached" (it was already 185c°. I know that because I used an external thermometer to check the temp at the hotend).
I will attach an example of the g-code just in case.
Many greetings and thanks in advance