As I have said elsewhere, APM, Thermo, Leckytech and NAR are all theory exams which benefit from study, the EKG is a practical exam, all about what you know and what you have done. If you have spent any time at all in the bilges grinding bilge valves, cleaning strum boxes, or pumping out bilges while on watch, you will have no problem. Sketch a block diagramme with the components of the system and connect them, showing flow. Don't forget the OWS monitor and SDNR valves! EK is Engineering Knowledge, all about what you have done, not about what you have read.
Same with a sketching a steering system. If that's all the question is, draw a tiller and rudder on a rowboat. That's a steering system. If, however, if it asks for an electro-hydraulic steering system, draw the one you know, what you have worked on, explain how the pump works, how the rams operate, what happens when the rudder is hit by a wave, what hunting gear is, how the telemotor works, how feedback is provided to the bridge. The Examiner is making sure you know enough that you won't do too much damage and won't kill anyone.
Concentrate on what you know, not on what you have to study to pass. "Study" should be on Exam technique, how to organize your knowledge, and this has been extensively covered in other topics here by JK and others. If you have to study subject matter, you shouldn't be writing the exam, get some more experience and pay attention to what you are doing this time. An experienced Engineer should be able to write the EKs cold, with no preparation, and have a reasonable prospect of passing them. (Yes, there are precedents.)
There's a reason you need a total of 60 months qualifying service to write 2nd Class, by that time, you should have enough experience on ships to know what you are doing. If you have the experience and the knowledge, go for it. If you don't, don't waste your time and money.
When writing the Exam, the guiding principles are K.I.S.S. and R.T.F.Q.
Discourage incest, ban country "music".