oops copied the wrong thing, meant to copy this.....

Here is how I set the tension whether I am using a new tensioner or not:

I do not use an Allen wrench on the tensioner as noted previously, I just let the tensioner expand all the way
Once the belt is installed, I place a .150" drillbit (or the nearest larger size I have) on the top of the tensioner body, and screw in the tensioner tool until it captures the drillbit between the tensioner body and tensioner pulley bracket. When the bracket is close to the drillbit, I start spinning the drillbit, and stop screwing in the tool as soon as the bracket stops it from spinning. In other words, I stop when the pulley bracket is just snug against the bit.
I place a flatblade screwdriver between the engine and tensioner pulley, and lightly pry up on the pulley
I torque the pulley down
I back off the tensioner tool several turns, and immediately check the tensioner gap - if it has gotten too small or too large right away, I redo the steps above, changing the pressure used on the screwdriver. If the gap looks OK, I spin the engine 6 turns and wait 15 minutes and check the gap again.
There are other ways to do this, but this works best for me

i didnt do any of that, i aligned all the marks, clamped the belt on and pulled the pin......