Pumpkin Ale

Now you made an interesting point and may not know it. Why not, if you are gonna add the pumpkin anyway, just add it to the primary fermenter. If you sanitize (and perhaps clean) the exterior of the can the pumpkin in the can should already be sanitary.

It would be interesting to take a low hopped pale ale and add a can of pumpkin with no spices to one fermenter and do nothing to the other and then determine if one could perceive the pumpkin other than visually. I’ve always felt the spices drive the flavor in most pumpkin beers, but it might be worth a while. I may actually try this the next time I crank out a Saison to see what happens. Thanks for the idea…

I kegged my pumpkin ale on 11/16 using the following recipe.
3 lbs Two row
3 lbs Maris Otter
1 lbs Victory
8 oz Cystal 60L
8 oz Rye Malt
3.5 lbs canned pure pumpkin puree (in the mash)
Handful of rice hulls
.25 oz Magnum 60 min
.25 oz Fuggles 30 Min
.25 oz EKG 30 min
1 t. cinnamon (5 min)
1/2 t. allspice (5 min)
1/2 t. ground ginger (5 min)
1/4 t. nutmeg (5 min)
1/4 t. clove (5 min)
WLP002 (1L Starter)

Single infusion mash at 151 (Post-Boil OG:  1.046).  I fermented for 3 weeks at 68 F (FG:  1.011), crash cooled to 40 F for two nights and kegged it.

I tasted it today (after 2 days of carbonating) and it is still a bit under carbonated as I would expect.  However, I am noticing so far it tastes watery.  Why would this be?

When you added your tincture to your keg, was it carbed up already?  I tasted mine and feel it needs a bit more spice, but it has been carbing up for a few days now.  Would I still be able to add a spice tincture?

Yes, mine was carbed although at a low level since it was only on the gas for a couple days when I did it. 
One thing I’ve found since is that even though I strained the tincture, there was enough finely ground spice that got through the cloth to bump up the taste a bit more after it was in the carboy. 
I tried a coffee filter first but it was just too slow and not really working.

I can’t see how it would hurt to add it after carbing.  Vent off the gas, open it up and add it.  May take a bit to get the tincture distributed unless you roll it around a bit which chould make it a bit gassy when you poured but that’s about all I can think would happen (assuming you don’t oxygenate the heck out of it).
Good luck.