Stern of a boat

The stern is the after end of a boat, the whole region at the back, and the ITTC dictionary takes it from the keel line up to the top of the hull. Anything toward it lies aft, so on the runabout above the motor sits aft of the transom and the helm sits well forward of the stern. Anything behind the boat lies astern, and a boat going astern is moving backward.

A place, a surface and a direction

Stern, transom and aft get used as if they meant one thing. Stern is a place, transom a surface, aft a direction. Federal boat regulations define the transom as the surface at the stern that projects or faces aft. A boat can therefore have a stern without any transom: a canoe stern comes to a point much like the bow, which makes the boat a double-ender.

What sits at the back of an outboard boat

The highlighted parts on the drawing are the ones you meet at the back of a typical outboard runabout. The outboard motor is a self-contained engine, gear case and propeller, mounted on the transom. The swim platforms on either side of it give you a low step for climbing aboard from the water. Low on the transom, the drain plug controls the draining of water from the hull. On its pole above the cockpit, the white light is an all-round light, visible over the full 360 degrees.

Other boats are driven from the stern in other ways. A sterndrive, also called an inboard/outboard, has its engine inside the hull, joined through the transom to a drive unit outside it. An inboard engine turns a shaft running out through the bottom to the propeller, and a rudder behind it steers.

Five stern shapes

The row of shapes below the drawing shows five sterns on hulls of one length, with the waterline at the same height in each. A transom stern stops at a flat or nearly flat surface across the back. A reverse transom leans the other way, forward at the top, so the stern slopes forward from the waterline to the deck. A counter stern carries a long overhang aft above the waterline, and a cruiser stern is rounded, with a convex profile and less flat surface at the back.

Compare the plan views as well as the profiles. The canoe and cruiser sterns narrow toward the back, while the transom and reverse transom keep much of their width to the end.