Transom (nautical)

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Transom of a larger commercial vessel

In naval architecture, a transom is either the surface that forms the stern of a vessel or one of the many horizontal beams that make up that surface (e.g., the "wing transom", etc.). Transoms may be flat or curved and they may be vertical, raked forward, also known as a retroussé or reverse transom, angling forward (toward the bow) from the waterline to the deck, or raked aft, often simply called "raked", angling in the other direction.[1][2] The bottom tip of the transom can be approximately on the waterline, in which case the stern of the vessel is referred to as a "transom stern", or the hull can continue so that the centreline is well above the waterline before terminating in a transom, in which case it is referred to as a "counter stern"[3] or "cutaway stern."[4]

Outboard motor mounted to the transom of a boat

On smaller vessels where an outboard motor is the source of propulsion, the motor is usually mounted on the transom, and held in place either by clamps or metal bolts that go through the transom. In this arrangement, all the power of the motor is transmitted via the transom to the rest of the vessel's structure, making it a critical part of the vessel's construction.[5]

The term is probably a corruption of Latin transtrum, a thwart, in a boat; equivalents are French traverse, croisillon, German Heckspiegel.[6]

The expression "over the transom" is rooted in the architectural meaning of the word.


  1. ^ "Taylor Made Systems: Glossary". Retrieved 2007-12-14.
  2. ^ Jordan, Richard (September 19, 2009). "Stern Styles and Transom Types". Retrieved April 25, 2010.
  3. ^ "Transom Stern". Maritime Dictionary. Retrieved 2007-12-14.
  4. ^ "Online Library of Selected Images". United States Navy History and Heritage Command. 17 March 2007. Retrieved April 25, 2011.
  5. ^ "How to determine the correct outboard shaft length". Retrieved 2007-12-14.
  6. ^ "Encyclopædia Britannica, 11th Edition: Transom". Online Encyclopedia. Retrieved 2007-12-13.