Yanmar 2GM20

The Yanmar 2GM20 is an inboard marine diesel engine manufactured by the Japanese company Yanmar Co. Ltd.. It is used in a wide range of sailboats and motorboats.

pecifications

It is a four-stroke, vertical, water cooled diesel engine. It is built around two cylinders (hence the "2" in 2GM20) of 75mm in length and 72mm 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. [Yanmar technical reference sheet]

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. [Yanmar technical reference sheet]

The engine delivers roughly 20 horsepowers (hence the "20" in 2GM20), for a weight of about 114 kg.

The engine is equipped with a starting motor (D.C. 12V, 1kW), 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 hot cooling water alarm and 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 again 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).

Water pump

The 2GM20 series uses either a seawater cooling system, or a freshwater cooling system (specified by the letter F). Seawater is pumped into the engine through a seawater pump (impeller type). In the engines equiped with a seawater cooling system, seawater is used to cool the internals of the engine directly. The engines equiped with a freshwater cooling system have an additional heat exchanger, where heat transfer occurs between the seawater and internal freshwater.

The impeller of the seawater can suffer from wear and tear, especially when run dry for some period of time, in which case it has to be replaced to avoid loss in the flow of cooling seawater, a potential source of engine overheating.

The seawater pump is rotated by a short belt linked to the crankshaft.

Fuel filter

An inline fuel filter is easily accessible from the front part of the engine. The filter allows to retain dust particules and separate water from diesel (as water is heavier than diesel, it will settled at the bottom of the filter), just before the diesel fuel enters the highly sensitive high-pressure fuel pump. Water inside diesel fuel can lead to rusting of the internals of the engine, as well as lubrification problems. The filter is made of a metallic mesh.

When the engine has to be bled because air has penetrated into the pipes (usually after running out of diesel), it will usually be necessary to bleed the diesel filter: the top vent is unscrewed so as to let excess air escape, while diesel fuel is pumped into the fuel filter with the manual fuel lift pump (just behind the yellow dipstick). The vent can be screwed shut when diesel fuel starts to gush out of it.

A primary fuel filter is usually installed upstream of the engine, so as to filter out the larger particules, and filter a larger quantity of water that might be present in the fuel.

Everytime a filter is disassembled or changed, it will be necessary to bleed it so as to remove excess air, again by opening the top vent so as to let diesel chase all the air (diesel fills up the filter either through gravity -usually the case for the primary filter- or with the help of the fuel lift pump -usually the case for the engine fuel filter-) and diesel starts to gush out. The vent should then be screwed shut.

New models

The 2GM20 and 3GM30 (three cylinder) series have now been superseeded in the Yanmar catalog by new lightweight and modernized engines, the 2YM15, 3YM20 and 3YM30. These new engines also feature simplified maintenance of the seawater pump and other services points, as they are now located on the front part of the engine. [Yanmar website [http://www.yanmar.com.au/marine/gm_series/gm_series.htm] ] These new engines also meet new Tier II emission standards introduced in the EU and the US in 2006. [ [http://www.yanmar.com.au/marine/gm_series/pdf/2YM15_TechData.pdf Yanmar technical data for the 2YM15] , [http://www.yanmar.com.au/marine/gm_series/pdf/3YM20_TechData.pdf 3YM20] and [http://www.yanmar.com.au/marine/gm_series/pdf/3YM30_TechData.pdf 3YM30] ]

Parts

Versions

*Yanmar 2GM20: Marine main engine (for export), seawater cooling, model codes: 128271 (S, N, G).
*Yanmar 2GM20-B: Marine main engine (domestic use), seawater cooling, model codes: 128271 (A, B, C).
*Yanmar 2GM20C: Saildrive engine, seawater cooling, model code: 128271 E.
*Yanmar 2GM20F: Marine main engine (for export), freshwater cooling, model codes: 128291 (S, N, G) [http://www.yanmar.com.au/superseded/20GM20F%20V/20GM20F%20V.pdf Pdf] .
*Yanmar 2GM20FC: Saildrive engine, freshwater cooling.
*Yanmar 2GM20FV: Marine main engine, freshwater cooling, equiped with compact V-drive marine gear KM3V. [http://www.yanmar.com.au/superseded/20GM20F%20V/20GM20F%20V.pdf Pdf]
*Yanmar 2GM20FVE

Notes

References

*Yanmar technical reference sheet [http://www.triton381.com/images/2gm20_2.gif]
*Yanmar brochure [http://www.simplicity-marine.com/pdf/Yanmar/123%20GM%20INBOARD.pdf Pdf]
*Yanmar Diesel Engine Parts Catalog (1995) 000Y00F5052

External links

* Yanmar Internet site [http://www.yanmar.com.au/marine/GMSeries/2GM/2gm20v.htm Yanmar GM series]
* Online parts catalogue for the Yanmar 2GM20 series [http://www.marinedieseldirect.com/catalogs/catalog.php?owner=mdd&manufacturer=Yanmar&model=2GM20&catalog=Y00F5052&printparts=&printservice=&printoperators=]