Okay, so the volume of such a sphere would be 8.71137 * 10^13 cubic light years. The mass of one cubic metre of pure water at maximum density is 1000 kilograms exactly. The volume of the sphere talked about in cubic metres would be: 7.37667 * 10^61 cubic metres. The mass of that sphere of pure water at maximum density would be 7.67667*10^64 kilograms.

The Schwarzschild Radius formula is: r[sub]s[/sub] = (2Gm)/(c^2) where r[sub]s[/sub] is the Radius, G is the gravitational constant, m is the mass, and c is the speed of light.

The Gravitational Constant is: 6.67384 * 10^-11 N m^2 kg^-2.
The mass is 7.67667*10^64 kilograms.
The speed of light is 299,792,458 metres per second.

So, according to Wolfram Alpha, the Schwarzschild Radius for this sphere is 1.14009×10^38 m^2/s.
Okay, that's not right. Let me use the other formula for the Radius. next post!