Another factor could be the choice of HEET as your fuel. The BTU/pound ratio is lowest of alcohol types listed in Fuel Comparisons at Zen Backpacking Stoves.

Using 2 TBSP (1oz) denatured (SLX), an aluminum Jim Wood cat stove on aluminum foil (to insulate from heat sinking to ground), and my Snowpeak Trek 900ti, I brought 25oz (as marked) of water to a rolling boil. Once there, it continued for another 1.5 minutes.

Hope this helps!

-Myke-