The more water the better heat transfer and therefore cools better.

Antifreeze is only there to drop freezing temp, raise boiling temp, and to inhibit rust.

 

You are absolutely correct Sir. That is why I am surprised that no one else caught that he has a 75% - 25% mixture.

 

Thanks for all the suggestions everyone, I'll siphon out the overflow tank about half way and fill with straight water and see how she goes.

 

To get to 50% water to 50% coolant from 25% h2o / 75% coolant you need to drain 35% of total volume of your mix and add water.
I was bored at work and did the math for you. I think it is correct.
You just gotta figure out what total volume is and drain 35% of that, and refill with water. I used distilled water.