Here is what you need to do in order to defeat this boss easily (as he can be very hard/frustrating on hard difficulty).
First, what you need to finish this battle is to jack him three times to destroy the three targets (as he automatically unjacks himself when you destroy one target), hopefully you start this fight with a jacked titan, if not, jack the EE-lectric and attack the rest of the enemies then attack Uka Uka with regular attacks, (even when he uses the red laser things, because your attacks can/will destroy them but dont get too close or he will use another attack).
Jack him the first time but DO NOT destroy any target yet, kill the remaining enemies instead and hit every target TWICE with regular attacks (the 3 machines you need to destroy to finish the level), now they all need one more hit to be destroyed, so walk towards the screen, turn around and aim at the leftmost one (using
), now hold
and as soon as you see/hear that he's throwing the red laser things, aim for the other two targets... you have to be kinda fast but if done correctly, all 3 targets will be destroyed and you wont have to jack him anymore.
Hope this is helpful as I found this battle to be really, really annoying.
EDIT: Found this video on YouTube, the quality is very poor but if you skip to 1:40 you can see how this method is done. Credit goes to achievementPredator on YouTube for making and uploading the video.