One of the essentials for a motor is something that can be burned to make it so that the motor is able to gain energy. In outboard motors for boats, the fuel being burned is typically gasoline which is either added to the engine of cycled through it from a gas tank that can be easily connected to the motor. A motor cannot run without burning some type of fuel.
Oil is another story entirely. A motor can run without oil and may sound just fine running without it. Unfortunately this can mislead people and make them think that it is alright for them to deprive the engine of oil on a regular basis. This is one of the biggest mistakes that you can make when using any kind of an engine.
Motor require oil to make it so that the moving parts inside of an engine can continue moving the way that they are meant to move. Without the outboard motor oil in a boats engine, the parts will scrape against each other and eventually cause significant problems. It is very important to always give your motor the proper supply of oil so that it can continue to run well.