Yanmar Marine Diesel Engine Model Codes

Sometimes it seems that Yanmar’s small marine diesel engines have crazy names. From the 3JH(B)E to the 4JH4E it’s sometimes hard to know what you’re dealing with. Don’t worry though – if you know what to look for, you can decode all the numbers and letters. Yanmar Engine Model Codes can tell you everything yopu need to know and you’ll soon be able to tell your 4JH3-T(B)E from your 4JH2-DT(B)E like a pro.

What do the Yanmar Engine Model Codes mean?

The nomenclature of the engine name codes on Yanmar small marine diesel engines tell us all the information we need to know about the engine. They explain;

  • The number of cylinders,
  • The engine family,
  • Some extra miscillaneous information relating to that family,
  • Specification upgrades such as the addition of a turbo,
  • Possibly some information about the stern gear.
Infographic explaining the Yanmar Engine Name codes
Yanmar Engine Model Codes

Where to find the code on a Yanmar Marine Diesel?

The plate on your engine should have all the necessary information. The transmission will have its own seperate plate with details about drive ratios etc.

If an engine does not have the Y in the beginning of the code, then it has a vertically mounted cylinder block. Y engines, such as the YSE12, had a horizontally mounted cylinder.

Engine Plate on a 2GM20-YEU

The numbers 1, 3, 4, and 6 indicate the number of cylinders. So for example, 3GM is a 3 cylinder engine with a GM type block. A 2GM is a 2 cylinder engine with a GM type block, and so on.

Note also that older engine families didn’t strictly follow the rules. The 1GMs, 2GMs and 3HMs, for example, existed prior to upgrading the cylinders to become 1GM10, 2GM20 and 3HM35 respectively.

Model CodeYears of productionVariants
Y Series Engines1967 - 1980YSB12
S Series1976 - 1980SB12
QM Series1977 - 19802QM (Japan only)
2QM20 (22 HP)
3QM (Japan only)
3QM30 (33 HP)
GM/HM Series1980 - 19831GM (7.5 HP)
2GM (15 HP)
2GMF (15 HP)
3GM (22.5 HP)
3GMF (22.5HP)
3GMD (22.5 HP)
3HM (30 HP)
3HMF (30 HP)
GM/HM Upgraded Series1983 - present*

* not all models
1GM10 (9 HP)
2GM20 (18 HP)
2GM20-YEU (18 HP)
2GM20F (18 HP)
2GM20FYEU (18 HP)
3GM30 (27 HP)
3GM30-YEU (27 HP)
3GM30F (27 HP)
3GM30F-YEU (27 HP)
3HM35 (34 HP)
3HM35F (34 HP)
YM Series2004 - present2YM15 (14 HP)
3YM20 (22 HP)
3YM30 (30 HP)
JH Series1983 - 19894JH-DTE (77 HP)
4JH-E (44 HP)
4JH-TE (55 HP)
4JH-THE (66 HP)
JH2 Series1989 - 19993JH(B)E (38 HP)
3JH2-T(B)E (47 HP)
4JH2-(B)E (51 HP)
4JH2-DT(B)E (88 HP)
4JH2-HT(B)E (76 HP)
4JH2-T(B)E (63 HP)
4JH2-UT(B)E (100 HP)
JH3 Series1999 - 20063JH3 (40 HP)
4JH3-DTBE (125 HP)
4JH3-HTBE (100 HP)
4JH3-T(B)E (75 HP)
4JH3E (56 HP)
JH4 Series2004 - present3JH4E (40 HP)
4JH4E (55 HP)