If you’re grabbing the cheapest fuel at the pump before backing down the ramp into Pittwater, you might be setting yourself up for a massive headache.
Ethanol-blended fuel (like E10) is fine for your daily driver, but it is absolute poison for marine outboards and carburettors. In fact, it's the number one reason we see engines stalling out, running rough, or refusing to start altogether. Here is exactly what happens inside your engine when you run cheap fuel.
The Water-Magnet Effect
Ethanol is hygroscopic. That’s just a technical way of saying it acts like a sponge, absorbing moisture right out of the humid coastal air. When your boat sits on the trailer or the mooring for a few weeks between runs, that ethanol is actively pulling water straight into your fuel system.
Phase Separation (The Engine Killer)
Once the ethanol absorbs enough water, it can't hold it anymore. The water and ethanol mixture literally separates from the petrol and sinks directly to the bottom of your fuel tank—which means it gets sucked straight into your carburettor bowl.
This mixture is highly corrosive. It attacks the aluminium housing and brass jets, eventually turning the remaining fuel into a thick, green, jelly-like varnish that completely chokes the microscopic passages inside the carb.
How to Protect Your Motor
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Skip the E10: Always pump Premium 95 or 98 (ethanol-free) into your boat tanks or jerry cans.
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Use a fuel stabilizer: If the boat is going to sit for more than three or four weeks, add a quality marine-grade fuel stabilizer to keep the petrol fresh.
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Run a water-separating filter: Install an inline water-separating fuel filter. It gives you a vital line of defence before contaminated fuel ever reaches your engine.
If your motor is already suffering the symptoms of bad fuel—hard starting, bogging down, or constantly dying at idle—spraying a cheap can of carb cleaner down the throat won't fix it. Once that green varnish sets in, standard sprays can't reach the internal blockages.
The only true fix is pulling the carburettor off, stripping it down, and running it through an industrial heated ultrasonic bath to blast the tiny jets completely clean from the inside out.