Oatmeal porter needs help!

Ok so brewed a partial mash oatmeal porter kit I got for the LHBS. I had a boil over right after I put the 60 minute hops in. It then bubbled over during primary fermentation ( I know just a mess of a brew day ). After 10 days I moved it to secondary for 20 days then I hooked it up to co2 and chilled for a week so after a total of five weeks I sampled it and it has an off smell to it. Sort of sour smell and a sweet after taste. I assume from the boil over losing my bittering hops.

So my question is ... I want to put a starbucks via in it to experiment. For those of you that don't know a via is an instant coffee pack that dissolve even in cold liquid. I think the coffee flavor would work with the oatmeal and maybe ad some bitterness.

Any thoughts?

So is this via a liquid or ground bean? If it's liquid, I imagine that you'd just get the flavor out of it. It may be strong, so I'd put some in then sample it. Add more if needed. If it's a ground bean medium and since it sounds like you're kegging, keep in mind that the grounds will sink and will be soaked up by the dip tube when you pour someone a pint.

One thing you may want to do is get bottle of some similar beer, pour it into a glass and finally add some of the instant coffee. Mix it a bit and then give it a try. It may give you a good idea as to how it will affect your beer!

As for this sourness; did you notice any white floating matter on top of your carboy or anything else unusual? In my experience, sourness is a sign of infection. Also, losing your bittering hops would not make the beer sour but instead make it seem sweeter or roastier because they are not there to balance out the malt flavors. When it bubbled over in the primary, where you very careful while cleaning it up? Did you sanitize everything before and after cleaning? These are some things you might want to think about.

Next time you see a boil over sneaking up on you, just take the kettle off the burners for a few seconds as it settles. Feel free to use your stirring spoon to keep the precious ingredients inside but don't stir the wort! Once it settles, it ought to stay down afterward so just plop it back on the coils. It's happened to me before but now I'm ready for them!