Sterndrive
A sterndrive or inboard/outboard drive (I/O) is a form of marine propulsion which combines inboard power with outboard drive. The engine sits just forward of the transom while the drive unit (outdrive or drive leg) lies outside the hull.
Operation
The drive unit (outdrive) carries power from the inboard engine, typically mounted above the waterline, outboard through the transom and downward to the propeller below the waterline.
The outdrive resembles the bottom half of an outboard motor and is composed of two sub-units: an upper containing a driveshaft connected through the transom to an engine which transmits power to a 90-degree-angle gearbox; and the lower containing a vertical driveshaft receiving power from the upper unit gearbox, transmitted through another 90-degree-angle gearbox to the propeller shaft.
The boat is steered by pivoting the outdrive, as on an outboard motor; no rudder is needed. The outdrive is pivoted up for trailer travel and between uses to avoid fouling.
Azimuth thruster
An azimuth thruster is a configuration of marine propellers placed in pods that can be rotated to any horizontal angle (azimuth), making a rudder unnecessary. These give ships better maneuverability than a fixed propeller and rudder system.
Types of azimuth thrusters
There are two major variants, based on the location of the motor:
Podcasts:
