A skeg is a fin-shaped part of the outboard motors used on small boats. These boat parts are situated beneath the boat's propellers, serving as protection for the propellers as well as the motor's gear case. A skeg also refers to a keel-like device on the stern of small water craft such as open-water kayaks, surfboards and windsurfers. In these cases, skegs help with navigation and control.
Skegs on outboard motors are commonly damaged when boats run into rocks and other underwater debris. As a result, repairing or replacing a skeg can be common and the complexity and cost associated can vary widely. Sometimes a simple welding patch job can repair small holes of 1.2 inches (30mm), but other times the entire skeg must be replaced with a more complicated welding job. Skeg guards, which are aluminum covers that can be bolted on to a motor's skegs to protect them, are commercially available and can help reduce potential damage.
In kayaks, the skeg doesn't help steer like a rudder; rather it helps "track" or keep the craft on course as the person in the kayak paddles. Kayaks are small and relatively light, making them vulnerable to wind and water currents. A skeg helps stabilize the kayak and keep it moving forward, which allows the paddler to more easily control navigation.
Whitewater kayaks, which generally are smaller and need to be more maneuverable, do not have skegs, but open-water or touring kayaks do have them. In most kayaks the skeg is retractable, allowing the paddler to control it with a cord in the kayak cockpit. Paddlers might retract the skeg when they want the boat to turn more easily. For the best control, skegs should be placed about one-third to one-half the distance from the cockpit to the stern.
In surfboards, use of a skeg was pioneered by surfing technology innovator Tom Blake, who added the skeg to his boards beginning in 1935. Use didn't catch on widely until the 1950s. Today, most surfboards have multiple skegs, or fins, as they're sometimes called because they resemble shark fins.
The word skeg has origins in Europe. It might have been derived from the Dutch word "sheg" or the Old Norse word "skegg," meaning beard or beak of the ship. The word also is the origin for the surfer slang "skegged," which means to be hurt by getting hit with someone else's surf board, usually with the skeg itself.