Yanmar Identification Help

Understanding YANMAR Engine Model Codes - A Brief Explanation:

Most engine model designations are on an engine data plate, on the front or the top of the engine. Some older engines have the data plate on the adapter plate between the engine and the gearbox .

Here are some examples of engine model codes and their meanings:

YSE8
Y= horizontal cylinder, lying down.
SE = engine model type or block type.
8=8 horsepower

If an engine model does not have the Y in the beginning, the engine has a vertical cylinder or cylinders.
The numbers 1, 3, 4, and 6 indicate the number of cylinders.
For example, 3GM is a 3 cylinder engine with a GM type block.


An engine with an enclosed cooling system containing fresh water and coolant, in turn cooled by raw water going through a heat exchanger, is a fresh water cooled engine. On engines that are either 'raw' or 'fresh', below 34hp, the fresh water cooled engine has the letter F in the model designation, i.e. a 3HM35F is a freshwater cooled engine. If the F is absent, it is a 'raw' water cooled engine.
The JH, LH, LP, LY, CX and KY family of engines are all freshwater cooled.

The letter C indicates the engine has a saildrive attached.
A -BE model is fitted with a down angle gearbox.
An M means the engine was shipped from the factory without a gearbox e.g. 6CXM-ETE
An -E is a normally aspirated export engine
A -TE, is a turbocharged, export model engine
An -ETE is extra turbocharged
A -HTE is highly turbocharged
A -DTE is deluxe turbocharged
A -UTE is ultra turbocharged
A -STE is super turbocharged
When the code has a Z, e.g., 4LHA-STZE, the engine is an inboard outboard model with a Mercruiser sterndrive or 'Z' drive.

Y Series
These horizontal models lay down in a low profile. The series was updated three times with the YSE being the earliest model, followed by the YSB and then the YSM. Either a 2:1 or 3:1 transmission. The models were sea-water cooled, singe cylinder, heavy duty. This series includes the following engines:

S Series
Vertical models, updated two times with the SVE engines followed by the SB. Single cylinder, 2:1 or 3:1 transmissions, sea water cooled, heavy duty. This series includes the following engines:

QM Series
The QM series was available either sea-water or fresh-water cooled. 2:1 or 3:1 transmissions. A designation of F near the end of the model means it is fresh-water cooled. F=Factory Fresh Water This series includes the following engines:

GM/HM Series
Introduced in 1980 and 1981 this series was a completely new generation of engines. Lighter, smaller, smoother and quieter than previous engines. An F designation on the model number indicates factory fresh-water cooling. 35 AMP alternators. This series includes the following engines:

GM/HM Bored Up Series
Similar to the earlier standard GM/HM series, these engines provide upgraded horsepower and a 55 AMP alternator (1GM10 35 AMP). Special Note: If your engine serial number starts with an "E" you must make sure that you use parts for the YEU engines. For example, if you have a 2GM20 with a serial number starting with E you actually have a 2GM20YEU. The (YEU) engines are European manufactured and now more common in the United States than the Japan built models. This series includes the following engines:

YM Series
Completely redesigned cylinder block and new combustion system. Indirect injection, fresh water cooled with heat exchanger, this new engine line complies with ETA Tier 2 and BSO Tier 2. Electric stop solenoid is standard. This series includes the following engines:

JH Series
Extremely smooth running. Two transmission possibilities were available – either a Hurth or 7 degree down angle B type. 80% of the parts for this series of engine are inter-changable since all four engines in the series used the same block. This series includes the following engines:

JH2 Series
Extremely smooth running. Horsepower upgrade over the previous JH series. Quiter and cleaner exhaust. A B designation on these engines indicate a down angle transmission. This series includes the following engines:

JH3 Series
Upgraded blocks, smaller overall size, smoother and quieter. Meets all new EPA requirements. This series is a replacement of the JH2 series. This series includes the following engines:

JH4 Series
Redesigned cylinder block and new combustion system. Produces 25% more torque with only a 10% increase in displacement. Lower running speed and less vibration reduce noise by five decibels. Complies with EPA Tier 2 emmissions. This series includes the following engines:

JH5 Series
New fuel system and new combustion system. Same block and RPM as JH4. Engine speed remains unchanged at 3000 RPM. Complies with latest EPA Tier 2 emissions.

LH Series
Extremely compact and lightweight. Very powerful. Transmission is a 7 degree down angle (bi-rotational). Also designed to cleanly replace gas V-8 engines. Larger Hp models. A=Built in USA. Available as both inboard and Mercruiser Stern Drive packages. This series includes the following engines:

LY Series
Introduced in 1992, this is the six cylinder version of the 4LH series. Lightweight, compact with excellent horsepower to weight ration. All models are the same size and weight. Smallest HP in its class.

Race-proven performance with startling power-to-weight capability and low-slung configuration. Extremely popular for repowering petrol-driven engines because of the flat-top, narrow profile of these diesels. The engines benefit further from outstanding fuel economy. This series includes the following engines:

LY3 Series
Introduced in 2005. Meets Tier 2 emissions. Electronic engine featuring 2 stage injectors, 24 valve cyliner head and is Tier II compliant. Smooth and robust engine with very high allowable continuous RPM (3198 RPM) UTC and STC engines are commercial rated for approved applications

LP Series
New mini-6 cylinder, super quiet, lightweight, designed for inboard and Merc sterndrive packages. Higher speed (3800 RPM). Many changes from Yanmar's traditional marine models. This series includes the following engines:

CX Series
Heavy duty, super smooth and quietest in this HP class. Commercial model with 4 valves per cylinder. Premium quality. This series includes the following engines:

LV Series
The best power-to-weight ratio in its class and compact size.

BY Series
Hailed as setting new standards for the boating industry, the leading-edge, second generation BY2 series engines continue at the same output as their predecessors but incorporate many upgrades, including the reprogramming of the ECU from torque to speed control, providing even smoother operation and better synchronisation on twin-engine applications.  Choose from shaftdrive or the hydrodynamic YANMAR ZT350 sterndrive.  These tough but lightweight, common rail electronic BY2 diesel meet the latest EPA and RCD emissions regulations. Developed in close association with car manufacturers BMW, the new Yanmar BY2 Series engines come in both four and six cylinder configurations and deliver car-like performance from common-rail diesel technology.

Thankyou to Yanmar International and Toad Marine Supply for this source of information