I worked on a seaplane dock as a teen. Radial engines use AvGas which is high octane gasoline. Turbine engines use Jet A which is a kerosene blend fuel.

Most de Havilland Beavers in my area are still radial engines due to the nostalgia that sells to tourists. Most companies have converted their de Havilland Otters to a turbine engine. I have seen turbine Beavers from other areas. You can visually identify the engine by the shape of the plane nose. A radial engine plane has a big, round, blunt nose and sounds like an idling drag racer with a deep glug glug glug noise. A turbine engine plane has a pointy nose and sounds like the high pitch whine of a jet engine.