saildrive

{{short description|Non-steerable propeller drive leg}}

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A saildrive is a transmission system for a boat whose inboard engine has a horizontal output shaft. The saildrive's input shaft is therefore also horizontal. That input shaft is geared so as to drive a vertical intermediate shaft extending downward through the hull. The intermediate shaft is then geared so as to drive a horizontal propeller shaft mounted on a skeg outside the hull.

The transitions from horizontal to vertical and then back to horizontal can be seen as a Z shape, and saildrives are indeed similar to the Z-drive transmissions used on larger vessels. The difference between a saildrive and a Z-drive is that a saildrive's propeller shaft is fixed in place, pointing aft, whereas a Z-drive's propeller shaft can be rotated to any azimuth.

Traditional sailboat transmissions consist of a simple horizontal output shaft extended rearward from the engine, through the stern via a stuffing box. The saildrive has several advantages over the traditional sailboat transmission: smaller horizontal size, no stuffing box to maintain, and the propeller is mounted horizontally instead of at a downward angle.

Saildrive also reduces propeller walk, reduces vibration, and is more efficient.{{cite web |url=http://www.boats.com/reviews/all-about-saildrives/ |title=All About Saildrives |last1=Sherman |first1=Ed |last2= |first2= |date= |website=www.boats.com |publisher= |access-date=15 March 2016 |quote=}}