Specifications
It is a four-stroke, vertical, water-cooled diesel engine. It is built around two cylinders (hence the "2" in 2GM20) of 75 mm in diameter and 72 mm in stroke, adding up to 0.635 liters in displacement: each cylinder is roughly the size and volume of a 300ml soft-drink can. The compression system uses a proprietary swirl-type pre-combustion chamber.
The continuous rating output at the crankshaft is 11.8 kW, and 3400 revolutions per minute (rpm). The maximum output at crankshaft is 13.4 kW, and 3600 rpm.
The engine delivers roughly 16 horsepower, for a weight of about 114 kg.
The engine is equipped with a starting motor (D.C. 12V, 1 kW), and an alternator to provide electricity and charge onboard batteries (12V, 55A).
The engine is typically activated by a key and a starting motor switch. Upon turning the key and pressing the starting motor switch, the oil pressure alarm will ring for about a second until the engine starts to run. The exit of cooling water from the exhaust into the sea (typically at the aft of the boat) should be checked at that time. After a few minutes, the hot cooling water alarm will sound if the cooling water does not get through the engine (as when the seawater cock has remained closed -most likely case- or if something is clogging the seawater tubing).
Read more about this topic: Yanmar 2GM20