Bulkhead leak

[Heres_doe_]

Should i use another gasket on the outside as well. I have the one on the inside but it's leaking just a bit. I only hand tightened it because I'm scared i mess it up using a tool. This is the overflow. You're looking from the inside out

 

[firechild]

A gasket on the outside probably won't help. You don't need much more than hand tightening (and overtightening can cause the gasket to twist causing leaks). Probably worth checking if there is something small caught in the gasket, give it a clean and try again. Once you have it hand tight, use a tool to tighten it slightly more and you should be ok.