Outboard motors, also known as OB’s, are the most common motor in the marine industry. The motor is mounted to the boat’s transom and is visible from the steering wheel. The horsepower range is between 1.5hp to 350 hp.
Outboard motors can be 2 stroke or 4 stroke motors. The 2 stroke motor will have the gas and oil mixed in the gas tank. The 4-stroke motor will mix the oil inside the motor. Outboards can have 1 to 4, and 6 cylinders.
The motor can be started with a pull start cord similar to a lawn mower for the smaller horsepower. They are often used for fishing and are steered sitting at the back by the transom using a tiller handle attached to the motor. Larger motors have a key start and are steered with a steering wheel at the front – usually used for vessels with more speed used for water sports or for cruising.
Outboard with Key Start Outboard with tiller handle
Sterndrive motors are also known as I/O’s, which stands for Inboard/Outdrive. The inboard engine is under the deck at the back of the boat and the outdrive comes out of the transom around the water line. The inboard and outdrive are connected with a universal joint that allows the outdrive to move, which changes the direction of the boat. These motors are always key start and steered at the steering wheel. I/O’s are all 4 stroke motors, with 4, inline 6, V6 or V8 cylinders. They can be purchased as single propeller or as dual propellers outdrives. I/O’s are usually higher horsepower engines. Since the sterndrive engine comes out of the lower transom, it doesn’t get in the way when fishing or trying to pull up to the dock. The price is usually attractive for a sterndrive and there are boat models that require only sterndrive motors.
Inboard motors, also known as IB’s, are marinized versions of Chevrolet and Ford automotive engines. They are placed either in the center of the boat or back at the transom under the deck. The propeller comes out of the bottom of the hull and is steered with a rudder placed behind the propeller at the back of the boat. They are often sold in either gasoline or diesel fuel options.
Inboards are great motors for extreme water sports. With the propeller underneath the boat, there is less opportunity for someone to get too close to the propeller while in the water or doing water sports