Hmmm. Okay. What kind of Processor do you have in your Computer?
Im not sure Furmark was the best tool to use, I think you should try using the 3dMark Vantage (free version). I would expect you to get a score of around 5000-6000 with one card.
With 2 cards you should hopefully get atleast 11000.
If you achieve 11000 on 3dMark Vantage then your SLI is working fine