Chapter 1: Know Your Boat
Types of Engines and Drives

Outboard Engines

• An outboard is a portable, self-contained package of an engine, gear case, and propeller– Rotating device that turns and powers a boat forward or backward that is attached to the transom – Vertical surface at the back of the hull of a boat.
• A growing number of outboard engines are of four-stroke design, but many are still conventional two-stroke engines that burn oil as a lubricant along with the fuel. New-technology two-stroke outboards are direct-injection engines and burn over 75% cleaner than conventional two-stroke outboards.
• Steering of outboard boats is controlled by a tiller– Lever used to turn a rudder to steer a boat or steering wheel that swivels the entire engine to direct propeller thrust.

Outboards have more power per pound of weight than do inboard engines.

Inboard Engines

• An inboard is a four-stroke automotive engine adapted for marine use. Inboard engines are mounted inside the hull's– Body of a vessel; basic structure or shell midsection or in front of the transom– Vertical surface at the back of the hull.
• The engine turns a drive shaft that runs through the bottom of the hull and is attached to a propeller– Rotating device that turns and powers a boat forward or backward at the other end.
• Many personal watercraft (PWCs)– A small vessel that uses an inboard jet drive as its primary source of propulsion, and is designed to be operated by a person or persons sitting, standing, or kneeling on the vessel rather than inside the vessel have two-stroke inboard engines that burn oil as a lubricant along with the fuel. New-technology two-stroke PWC engines are direct-injection engines and burn cleaner than conventional PWC engines.
• Steering of most inboard vessels, except PWCs and jet-drive boats, is controlled by a rudder– Steering device, usually a vertical blade attached to a post at, or near, the stern of the boat behind the propeller.

Inboards have automotive engines adapted to operate in marine environments.

Stern Drives

• Stern drives are known also as inboard/outboards (I/Os) because they combine features found on both inboard and outboard engines. Stern-drive engines are four-stroke automotive engines adapted for marine use and are mounted inside the boat.
• A stern-drive engine is attached through the transom to a drive unit (also called an "outdrive") that is essentially the lower unit of an outboard. The engine turns a drive shaft that is attached to a propeller at the other end.
• Steering of stern-drive boats is controlled by the outdrive, which swivels like an outboard engine to direct propeller thrust.

Stern drives have quieter and more fuel-efficient engines.