See Fig. 13 on page 12 - it shows the water level adjustment.
http://www.u-line.com/data/pdfs/30098_Rev31.pdf
Turning the screw in the (minus) direction will reduce the amount of water coming into the mold. But that probably won't solve the problem. It sounds more like a bad microswitch - on the opposite side of that metal plate. The screw adjustment determines how long that microswitch keeps the water valve open. When the microswitch goes bad, the water valve usually stays on (open) all the time. Replacing the microswitch will more often than not, solve the problem. It is a standard microswitch (single pole-double throw) that can be bought at any Radio Shack or other electronics store.
Turn off the machine, and thaw it out. Then remove the 3 mounting screws that hold the metal plate to the "black box" behind it. You can then lean the metal plate down from the top, to access the rear of it. Be sure to note which way the microswitch is mounted, and which wires connect where. It is called the water valve switch, in the U-Line vernacular, but again, it is a standard microswitch that you can buy for about 5 bucks. Remove and replace the switch and reconnect the wires.
To get the metal plate back in place is a little tricky - you have to first turn the ejector finger thingy, so that the flat on the end of it lines up with the flat in the mating hole in the rotating cam (usually red, sometimes white) on the back side of the plate. Also, there is a spring that controls the wire bail arm that checks the ice cube level in the ice bucket - the "tang " from this spring must go through a little hole in the metal plate - this is important, and is often overlooked. The other end of the spring simply presses against the side of the black mounting box. Once you've got the spring's tang and the flat on the ejector fingers in place, you can press the plate assembly into position and re-install the 3 screws. Don't tighten them all the way just yet.
Now turn on the machine and see if it works - it should. After it's run a few cycles, you can tighten the screws the rest of the way and replace the cover over the plate assembly. You may have to re-adjust the water level adjusting screw afterwards, because you may not be getting enough water into the mold now.