- Stern drives are known also as inboard/outboards (I/Os) because they combine features found on both inboard and outboard engines. Stern-drive engines:
- Are four-stroke automotive engines adapted for marine use and...
- Are mounted inside the boat and...
- Are quieter and more fuel-efficient engines.
- A stern-drive engine is attached through the transom to a drive unit (also called an "outdrive") that is essentially the lower unit of an outboard. The engine turns a drive shaft that is attached to a propeller at the other end.
- Steering of stern-drive boats is controlled by the outdrive, which swivels like an outboard engine to direct propeller thrust.