There is no reason to run leaded fuel in a outboard 2-stroke engine.

I agree, the only other functions of lead (beyond boosting octane) was to
lubricate valves and foul plugs. Since you don't have valves and the octane is
boosted in other ways I don't see a problem with running unleaded fuel that has
enough octane. My 1990s vintage engine wanted (US) mid grade (~89)