okay the differences in the rates...(forgive any typing errors, my 10 month old is on my lap trying to help) and this is only for a Sub, i was never a skimmer
Machinists Mate (MM)- These guys, as you know, are the mechanics. They repair all the mechinical equpment. The Main Engines, Reduction Gears, Turbines. They stand the watches of AMR2LL, ERUL, and ERLL (S5W), and ERUL, ERML, ERLL, and ERF (S8G). The run the 12k (or 8K) which makes the water for the sub. On a S8G there is also a 3K. They also run the AC units, big R114 units, dont ask me how big..i dont remember. They do all the maintenance and watch standing for this equiment. In order to be an ELT or a Boat Welder you have to be an MM.
Electricians Mate (EM)- They are the Electricians. They are the only ones on the boat. They run the electric plant, which means they have a big panel in manuevering where they open and close the major feeder breakers, and control the voltage and frequency on the AC end and the voltage on the DC end. They also control the DG when it is running...once the A-ganger gets it all "warmed up and ready for electrical loading". They also do most of the work on galley equipment. The ovens and so forth, if any of that breaks it is their job. On a trident they also have the 400Hz generators and the 10KW's, which are for the nav dept. They have all the motors on the entire boat. And they also have the mist collectors in the sub. They definately have the most equipment. They are also responsible to bring on shore power in port. They are the only rate (as far as i remember) who can qualify BCE.
Electronics Technician (ET)- WE have the most schooling, and end up with the cleanest jobs. We are responsible for all the instrumentation for Primary and Secondary systems. NI's, PPI's, SQWLC (Squiggle). The maintenance we do is not a whole lot, but it takes a couple hours usually for it all. lots of paperwork to be filled out and signed. Very political job. we also have some mechanical stuff we work on, the feed flow equipment and guages are ours. The ET's are the only ones who can qualify RO. But anyone can qualify SRO. The RO's have to do the Critical Rod Height Calculations, and the Calorimetrics. Both jobs you learnt to dread. Most of our stuff is done with tweakers, little screw drivers.