Oil/gasoline mixture. No requirement that there needs to be lead in the gas, as far as I've ever heard.

Well, I know it's got oil mixed in. Presumably the leaded fuel requirement is only for four-strokes though, since two-strokes can't run on leaded?

It's kind of an orthogonal issue. Oil is needed in the fuel for two-strokers with crankcase ventilation for lubrication. Lead is needed to boost octane. But your old outboard engine is most likely a very simple low compression engine that doesn't need particularly high octane, so can run just fine on regular car gasoline (preferably without ethanol, but again a slightly different issue) mixed with the two-stroke lubricating oil.

I know how they work, I'm just wondering if 2-stroke aero engines get a pass from using leaded fuel since they run for about ten minutes before the lead fouls the plug.

> 2-stroke aero engines

Which 2-stroke aero engines are you thinking of?

> get a pass from using leaded fuel since they run for about ten minutes before the lead fouls the plug

Huh? Before unleaded automotive gasoline became the norm, all kinds of 2-stroke engines ran on leaded gasoline just fine.