The Yanmar 2GM20 is a series of

inboard An inboard motor is a marine propulsion system for boats. As opposed to an outboard motor where an engine is mounted outside the hull of the craft, an ''inboard motor'' is an engine enclosed within the hull of the boat, usually connected to a prop ...

marine

diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-cal ...

manufactured by the Japanese company Yanmar Co. Ltd. It is used in a wide range of sailboats and motorboats. The 2GM20 is out of production and has been superseded by the newer Yanmar 3YM20 series.

Specifications

It is a

four-stroke A four-stroke (also four-cycle) engine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either direct ...

, vertical,

water-cooled Cooling tower and water discharge of a nuclear power plant Water cooling is a method of heat removal from components and industrial equipment. Evaporative cooling using water is often more efficient than air cooling. Water is inexpensive and n ...

diesel engine. It is built around two

cylinders A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an in ...

(hence the "2" in 2GM20) of 75 mm in diameter and 72 mm in

stroke A stroke is a disease, medical condition in which poor cerebral circulation, blood flow to the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemorr ...

, adding up to 0.635 litres in displacement: each cylinder is roughly the size and volume of a 300 ml soft-drink can. The compression system uses a proprietary swirl-type pre-

combustion chamber A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process. Intern ...

.Yanmar technical reference sheet The continuous rating output at the

crankshaft A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecti ...

is 11.8 kW, at 3400

revolutions per minute Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines. Standards ISO 80000-3:2019 defines a unit of rotation as the dimensio ...

(rpm). The maximum output at the crankshaft is 13.4 kW, at 3600 rpm. The engine delivers roughly 16

horsepower Horsepower (hp) is a unit of measurement of power, or the rate at which work is done, usually in reference to the output of engines or motors. There are many different standards and types of horsepower. Two common definitions used today are t ...

, for a weight of about 114 kg. The engine is equipped with a starting motor (D.C. 12V, 1 kW), and an

alternator An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature.Gor ...

to provide electricity and charge onboard

batteries Battery most often refers to: * Electric battery, a device that provides electrical power * Battery (crime), a crime involving unlawful physical contact Battery may also refer to: Energy source *Automotive battery, a device to provide power t ...

(12 V, 55 A). 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 Exhaust, exhaustive, or exhaustion may refer to: Law *Exhaustion of intellectual property rights, limits to intellectual property rights in patent and copyright law ** Exhaustion doctrine, in patent law ** Exhaustion doctrine under U.S. law, in ...

into the sea (typically at the

aft "Aft", in nautical terminology, is an adjective or adverb meaning towards the stern (rear) of the ship, aircraft or spacecraft, when the frame of reference is within the ship, headed at the fore. For example, "Able Seaman Smith; lie aft!" or "Wh ...

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).

Water pump

The 2GM20 series uses either a direct seawater cooling system, or an indirect freshwater cooling system (specified by the suffix letter F i.e. 2GM20F).

Seawater Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has appro ...

is pumped into the engine through a seawater

pump A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy. Pumps can be classified into three major groups according to the method they ...

( impeller type). In the engines equipped with a direct seawater cooling system, seawater is used to cool the internals of the engine directly. The engines equipped with a fresh water cooling system have an additional

heat exchanger A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct conta ...

, where heat transfer occurs between the seawater and internal

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does incl ...

. The impeller of the seawater pump 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. A particularly difficult problem in tropical waters is jellyfish. Their tentacles can be sucked into water intakes. In extremes, it is possible for the rubber exhaust hose to catch fire, the plastic silencer to melt and the head-gasket to fail. In colder waters, boats are far less likely to meet such problems. The solution is to have a large basket-type water strainer and overheat alarms (standard on most Yanmar engines) The seawater pump is rotated by a short

belt Belt may refer to: Apparel * Belt (clothing), a leather or fabric band worn around the waist * Championship belt, a type of trophy used primarily in combat sports * Colored belts, such as a black belt or red belt, worn by martial arts practiti ...

linked to the crankshaft.

Fuel filter

An inline

fuel filter A fuel filter is a filter used to screens out foreign particles or liquids from the fuel. Most internal combustion engines use a fuel filter, in order to protect the components in the fuel system. Filters for foreign particles Unfiltered fuel ...

is easily accessible from the front part of the engine. The filter retains solid particles and separates water from diesel (as water is heavier than diesel, it will settle at the bottom of the filter), just before the diesel fuel enters the highly sensitive high-pressure fuel pump. The water inside diesel fuel can lead to rusting of the internals of the engine, as well as lubrication problems. The filter element is made of fluted paper with metal end caps. 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 the excess air escape, while diesel fuel is pumped into the fuel filter with the manual fuel lift pump (just behind the yellow

dipstick A dipstick is one of several measurement devices. Some dipsticks are dipped into a liquid to perform a chemical test or to provide a measure of quantity of the liquid. Since the late 20th century, a flatness/levelness measuring device trademarke ...

). 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 particles and filter a larger quantity of water that might be present in the fuel. Every time 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 superseded in the Yanmar catalog by the 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. These new engines also meet new Tier II emission standards introduced in the EU and the US in 2006.Yanmar technical data for the 2YM153YM20
an
3YM30
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Parts

Image:Yanmar Injectors.JPG, Yanmar 2GM20

injector An injector is a system of ducting and nozzles used to direct the flow of a high-pressure fluid in such a way that a lower pressure fluid is entrained in the jet and carried through a duct to a region of higher pressure. It is a fluid-dynamic ...

s. Image:High pressure fuel pump.JPG, Yanmar 2GM20 high pressure fuel pump. Image:Oil filter.JPG, Yanmar 2GM20 oil filter. Image:Fuel lifting pump.JPG, Yanmar 2GM20

(yellow) and fuel lift pump (top). Image:Sea water cock.JPG, Yanmar 2GM20 cooling seawater

cock Cock or cocks most commonly refers to: * Cock (bird) or rooster, a male of any bird species * Cock (slang), a slang term for the penis Cock or cocks may also refer to: Names * Cock (surname) * Cocks (surname) Places * Cocks Glacier, Ross ...

(in closed position).

Applications

CS 34 The CS 34 is a Canadian sailboat, that was designed by Tony Castro and first built in 1989. The design is out of production. Production The boat was built by CS Yachts in Canada and is derived from the MG 335 also designed by Castro and bu ...

* Dana 24 * Freedom 30 *

JOD 35 The JOD 35 or Jeanneau One Design 35 is a French sailboat that was designed by Daniel Andrieu as an one design Sailing (sport), racer and first built in 1991. The JOD 35 was the one design class boat for the Tour de France à la voile from 199 ...

* Menger Cat 23 * Morgan 32 *

Pearson 28 The Pearson 28 is an American sailboat, designed by William Shaw and first built in 1975. The Pearson 28 was replaced in the company product line by a new Shaw design, the Pearson 28-2, introduced in 1985. Production The Pearson 28 was bui ...

* Sun Fast 31 * Sun Odyssey 31

Versions

*Yanmar 2GM20: Marine main engine (for export),

seawater Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has appro ...

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),

cooling, model codes: 128291 (S, N, G
Pdf
*Yanmar 2GM20FC: Saildrive engine, freshwater cooling. *Yanmar 2GM20FV: Marine main engine, freshwater cooling, equipped with compact V-drive marine gear KM3
Pdf
*Yanmar 2GM20FVE

Notes

References

*Yanmar technical reference shee

*Yanmar brochur
Pdf
*Yanmar Diesel Engine Parts Catalog (1995) 000Y00F5052

External links

{{commons category, Yanmar 2GM20 engine * Yanmar Internet sit

* Online parts catalogue for the Yanmar 2GM20 serie

Engines by maker Marine diesel engines