Entry & progression
Your outboard entitlement is unlimited propulsion power at every MED grade - including Grade 3. The kW ceilings apply to inboard engines only. This is the most counter-intuitive fact in the Australian engineering system, and almost nobody teaches the machinery behind it.
Read the schedule again. MED Grade 3: chief engineer, inboard under 500 kW - outboard, any power. Grade 2: inboard under 750 kW - outboard, any power. Grade 1: inboard under 1500 kW - outboard, any power. Even Engineer Class 3 near coastal permits chief engineer on outboard-engined vessels with unlimited propulsion power.
The power ceiling that governs your entire career simply does not apply to outboards. A quad-outboard patrol boat or charter vessel with a very large total installed power is, in certification terms, available to a certificate you can hold at sixteen with twenty days at sea.
TIP — This shapes where the work is Australia runs an enormous outboard-powered commercial fleet - dive boats, charter and fishing vessels, tour operators, survey and patrol craft, and yacht tenders. If you are starting at MED 3 and want responsibility early, outboard work is where a fresh certificate carries the most authority per day of sea service.
It also means the outboard is worth learning properly. Most engineering training treats it as an afterthought. The certificate schedule does not.
What an outboard actually is
A complete propulsion package on a bracket: engine, gearbox, propeller, steering and trim in one removable unit. Modern commercial outboards are overwhelmingly four-stroke petrol, though large two-strokes with direct injection remain in service. The combustion cycle is a petrol cycle - spark ignition - which makes it the one place in this course where you are not dealing with a diesel.
Cooling - the thing that kills them
An outboard is raw water cooled, and it draws its water through small intakes on the leg, low down, right where the sand and weed are. The water is lifted by a rubber impeller in the gearcase and pumped up through the powerhead. It exits, visibly, through the telltale - the little jet of water squirting out of the cowling.
CAUTION — No telltale means stop the engine That jet of water is your only external evidence that the cooling system is working. If it stops, or thins to a dribble, the impeller has failed or the intakes are blocked - and an outboard will destroy its powerhead in minutes.
Stop it. Check the intakes on the leg for a plastic bag, weed or sand. If they are clear, the impeller has gone. Impellers on outboards are a scheduled replacement item, not a run-to-failure item, and the schedule is in the manual for a reason.
The rest of what breaks
- Fuel - petrol goes stale, and ethanol-blended petrol absorbs water and attacks older fuel lines. Water in the fuel is the number one no-start on an outboard.
- Gearcase oil - a small drain and fill. If the drained oil is milky, water has got past the propeller shaft seal, and the gearcase will fail if you run it. Milky gearcase oil is a stop-work finding.
- Corrosion - the whole unit lives in salt. Anodes are sacrificial and must be checked and replaced. Flush with fresh water after every salt-water trip - and this is the single highest-value ten minutes of maintenance an outboard ever gets.
- The propeller - dinged, bent or wrapped with rope. Check it, and check for fishing line wrapped around the shaft behind it, which cuts the seal and lets water into the gearcase.
- Trim and tilt - hydraulic, and it leaks like any other hydraulic system.
Working on them safely
Petrol, not diesel. The vapour is heavy, it sinks into a bilge, and it is explosive in a way diesel is not. Ventilate before you start, and treat a petrol leak as an emergency, not a housekeeping job. And never run an outboard out of the water without a supply to the intakes - the impeller is gone in seconds.