Entry & progression
Engineer Class 1 is the ceiling. Nothing in the Australian engineering system sits above it. The prerequisite is Engineer Class 2, and there is no way round that - Lesson 1.2. This is a merchant certificate, because Australia issues no yacht engineering certificate at all.
An AMSA Engineer Class 1 certificate of competency entitles you to serve as chief engineer, second engineer or engineer watchkeeper on a vessel powered by main propulsion machinery of any propulsion power, in any operating area (Marine Order 72, Schedule 1). It also covers electrical, electronic and control engineering duties, and Able seafarer - engine rating duties. There is no higher engineering grade to climb to.
Any power - of the kind stated on the certificate
Read the entitlement again, because it has a limit inside it. Every AMSA engineer certificate is issued for a kind of propulsion power: Motor, Steam, or Steam and Motor (MO72 s8). "Any propulsion power, any operating area" is true only for the kind printed on your certificate. A Motor Class 1 is not a steam ticket. Sea service, too, must be performed on vessels using propulsion of the kind for specified portions of the qualifying time - see Lesson 1.3.
NOTE — Kilowatts, never gross tonnage Australian engineering certification is scoped in kilowatts. There is no gross tonnage figure anywhere in MO72 and none on any AMSA engineer page. The numbers that matter are 750 kW and 3000 kW. If you find yourself writing "Engineer <3000 GT", stop - no such certificate exists.
What Class 2 already gave you
Be precise about what Class 1 adds, because the common belief that "you need Class 1 to be chief" is simply wrong below 3000 kW. Engineer Class 2 is already a chief engineer ticket up to <3000 kW, in any operating area - and second engineer or watchkeeper at any power. What Class 1 adds is the top of the scale: chief engineer with no kilowatt ceiling at all.
The honest framing
This is a merchant ticket. It is a merchant ticket because Australia does not issue a yacht engineering certificate. Marine Order 74 - the yacht order - creates four grades, and all four are deck. Its stated purpose is competence "to be a qualified master or deck officer". The word yacht does not appear anywhere in Marine Order 72.
There is no AMSA equivalent of the MCA's MEOL(Y), AEC, Y4, Y3, Y2 or Y1. Nothing. So an Australian yacht engineer climbs the merchant ladder - Engineer Watchkeeper, then Engineer Class 2, then Engineer Class 1 - alongside the engineers on bulk carriers and tankers, against the same kilowatt thresholds and the same orals. That is not a complaint. It is the system, and you should understand it before you spend three years inside it.
TIP — If you want a yacht-specific engineering ticket, it is not an AMSA product The yacht engineering ladder is an MCA one - MEOL(Y), AEC, Y4, Y3, Y2, Y1 - and it is covered by the MCA Engineering courses already in this library. Many Australian yacht engineers hold a British ticket for exactly this reason. Read those courses before you commit to the MO72 route.
The Electro-technical Officer is a sideways move
AMSA's Engineer Class 1 page notes that with further sea service and study you may qualify for an Electro-technical Officer certificate. That is sideways, not up. ETO entitles ETO duties on a vessel of any propulsion power in any operating area, plus Able seafarer - engine rating. It is a different branch of the department, not a rung above the chief. Nothing sits above Engineer Class 1.