17 outside and I just have water, no anti freeze, am I OK?

As @JPhi1618 says, if you mean 17 degrees Farenheit, then no, as the water in the block will freeze, and expand - likely causing damage to the engine, and at the very least pushing out the core plugs - it won't matter if it's one night or the whole winter, the damage will occur as soon as the water freezes.

If you mean 17 degrees Celcius, then yes, of course it's fine (but then you probably wouldn't be asking!)