1997 Mercruiser 5.7L carburator throttle plate issue

[gica]

So I took the 2 barrel carburetor off, it is the 2 piece one. I took it all apart and I got to the throttle plates and took out 3 screws fine the 4th of course broke inside. Drilled it out and re-tapped with the M3x0.5mm tap. The hole is a little bigger on both ends but inside in the tap area seems to be ok don't know if 100% untouched by the drill but the M3 bolt screws on and tightens also. My question is what do I do to make sure the bolt stays on? Red Loctite? I can also put a nut at the end that comes out? Can I use any bolt or does it have to be a special material? I am including pictures.