A MED 2 qualification will enable you to act as Engineer on a vessel  <500kW < 200 from land.
For most vessels an MED 3 qualification will be adequate, however, if you are offshore and something happens to your engine or machinery it helps to know as much as possible about the engine and machinery on board. A MED 2 will also give you additional knowledge and skills to maintain your vessel. It is therefore recommended to go on and gain MED 2 even though most vessels you end up working on may only require a MED 3.
To qualify for the Certificate of Comepetency you will need 12 months seatime which includes engineering duties.
To enrol in the MED 2 course click HERE

To gain the Certificate of Competency see additional information from NSW Maritime HERE