Marine Engine/Drive Variations

Stern Drive (Inboard/Outboard, Outdrive) Engine

The engine is mounted inside the boat. The transmission/drive unit is outside of the boat, attached to the transom. The engine and drive unit are joined by a torque coupler and universal joint. Moving the drive unit steers the boat.

Inboard Engine

The engine and transmission/drive unit are inside the boat. A drive shaft is connected at the rear of the transmission and is run out of the hull through a sealing unit. The propeller is connected directly to the drive shaft and the in-water end. A seperate rudder steers the boat.

V-Drive Engine

This is very similar to the inboard, but slightly modified. The engine is mounted with the front (pully end) facing the stern (rear) of the boat. The transmission faces the bow (front) of the boat (see illustration: note that the back of the engine is facing the front of the boat). With the use of a universal joint on the end of the transmission, the drive shaft is directed stern-wards under the engine and through the hull. The propeller/rudder arrangement is the same as in a standard inboard installation.

Jet Drive Engine

Less common than all other configurations, a jet drive consists of an engine mounted inside the boat that is attached to a high speed pump which draws in water through an intake grate, increases its velocity, and forces it out through a directionally adjustable nozzle which is mounted outside the boat. Changine the direction of this nozzle steers the boat.