Do I need plumber putty or would the already existing rubber gasket seal this sink leak if installed properly?

Question

I had working kitchen sink until today when I had to remove and reattach sink garbage disposal. I am trying to figure out what is the quickest, but still acceptable solution to fix the leak that I just caused.
In most videos I have seen that plumber putty is applied form inside of the sink and nothing else. I suppose I disturbed it.
But in those videos that use plumber putty I have never seen anyone use a rubber gasket. However, my sink has a black rubber gasket installed from the outside of sink as can be seen here on top of the flange:

Unfortunately, in my case the Moen 3 bolt sink flange has only 2 out of 3 bolts. Not sure why one bolt is missing.
So my questions are:

Do I still need plumber putty if I have this gasket? Maybe I rather need to install the 3rd bolt and then rubber gasket would prevent any leaks once even pressure is applied?
If I still need to apply plumber putty, then can I silicone caulk or paste or anything else?

Update#1 some users said they could not see the gasket in the original picture. So I disassembled the Moen Garbage Disposal Flange. I am still not sure that I understand what is the purpose of that gasket from the bottom as garbage disposal top is already rubber and it pushes against the bottom of tall cylindrical part ensuring seal on bottom. And on the top there is plumber putty making seal. Could it be that this rubber gasket was actually intended to be used as substitute for plumber putty? I imagine that if in previous configuration the plumber putty would fail then water would simply still flow around this rubber gasket serving no purpose at all.

tnknepp · Answer

By having one bolt missing you actually prevent a seal from being made.  The two bolts you have only apply pressure on one side of the flange, effectively separating it on the other side.  I doubt you will ever get a reliable seal under this scenario.  As Solar Mike recommended, install the third bolt.
Regarding plumber's putty: the putty is a good idea because it is flexible and is not susceptible to cracking the same way a rubber gasket is.  That being said, whether you use putty or gasket ultimately comes down to the fitting type.  Fittings that have a lot of surface area (and are not pressurized) like the strainer basket are ideal for putty.  On the other hand, if the surface area of the seal is small then a gasket will get the better seal...provided it has all the bolts.
From your picture I cannot tell where the gasket is (maybe I can see it if I squint) but I'd say that if it came with a gasket then you need a gasket and you need that third bolt.
Regarding use of silicone: I advise against it.  It may get a good seal (may not!), but it is designed as a more "permanent" solution.  If you ever take the disposal off then you will have to clean all the silicone off before reinstalling otherwise you may not get a good seal.

Do I need plumber putty or would the already existing rubber gasket seal this sink leak if installed properly?

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