SEPP contributions CAN be a max of 25% of W-2 wages, 3% max sounds more like a SIMPLE.  

Which one are you actually talking about?  Altho, you can do 3% for the SEPP if ya' want 🙂   Like Susan says, the same %% has to be used for EE and for owner.

And the SEPP for the owner/Sch C actually ends up being just a bit less than 20% of the net Schedule C when you work thru the math (due to SE tax adjustment).