Nitro boats are primarily direct drive. This means when the engine is running, the prop is spinning. Historically, nitro boats are the fastest. The advantages to nitro boats are their speed and unlike electric powered craft, these have full power until the tank is dry. The disadvantages are that they can be loud, and you must be cautious of the spinning prop.
Nitro boats are available in various hull designs and material.
These are commonly called weed-wacker boats. These engines use the same gasoline and oil mixture as your household weed-wacker. These boats tend to be the largest, most expensive of all boats. They are available with direct drive or with a centrifugal clutch. With the clutch, the prop is not spinning when the engine is at an idle.