Yanmar 1GM Series Marine Diesel Engine

Image of Yanmar 1GM Marine Diesel Engine
Yanmar 1GM10

The 1GM / 1GM10 is a stalwart of the Yanmar range, truly representative of Yanmar’s famed reliability through simplicity. There are two main model variants of the Yanmar 1GM/1GM10 in circulation. Yanmar upgraded the 1GM to the 1GM10 some time in the late 1980s. The difference between the earlier and later models is in the displacement and operating rpm of the engine (and resulting horsepower developed). See the table below for exact specs.

Idle (no-load) speed (rpm)850850
Full load speed (rpm)37503825
Fuel Injection Timing25° before TDC15° before TDC
Valve Clearance0.2 m (0.008 in.)0.2 m (0.008 in.)
Oil Capacity1.3 litres / 1.4 qt1.3 litres / 1.4 qt
Num of Cylinders11
Displacement293 cc / 17.9 cu. in.318 cc / 19.4 cu. in.
Horsepower6.5 hp @ 3400 rpm8 hp @ 3400 rpm
GearboxKM2AKM2C or KM2P
Gearbox Ratio2.21, 2.62 or 3.222.21, 2.62 or 3.22

How heavy is a Yanmar 1GM10 Diesel Engine?

The raw-water cooled Yanmar 1GM10, complete with KM2P transmission weighs 76 kg (167 lbs). The older 6.5 HP 1GM weighed 71 kg (157 lbs) with the gear removed.

Components of the Yanmar 1GM – starboard side

Diagram of Yanmar 1GM Marine Diesel Engine starboard side
Yanmar 1GM starboard side
  1. Nameplate
  2. Thermostat cover
  3. Fuel injection pump
  4. Idle adjustment
  5. Oil filler cap
  6. Fuel injection limiter
  7. Engine stop level
  8. Crankshaft V-pulley
  1. Seawater pump
  2. Oil filter
  3. Regulator handle
  4. Fuel lift pump
  5. Dipstick
  6. Mounting flange
  7. Mixing elbow
  8. Fuel filter

Components of the Yanmar 1GM – port side

Diagram of Yanmar 1GM Marine Diesel Engine port side
Yanmar 1GM Port side
  1. Decompression lever
  2. Fuel injection valve
  3. Intake silencer
  4. Tachometer sensor
  5. Marine gear dipstick
  1. Marine gearbox
  2. Output shaft coupling
  3. Shift lever
  4. Starter motor
  5. Alternator

Specifications of the Yanmar 1GM10 Marine Diesel Engine

FeatureYanmar 1GM10
Configuration4-stroke, vertical, raw water-cooled diesel engine
Maximum output at crankshaft6.7 kW@3600 rpm
9 mhp@3600 rpm
at a fuel temperature of 25° C.
Displacement0.318 litres
19.41 cu. in.
Bore x stroke 75 mm x 72 mm
2.95 in x 2.83 in
Combustion systemIndirect injection [special swirl type pre-combustion chamber]
Starting systemElectric starting 12V - 1.0 kW with manual combination
Alternator12V – 40A
Cooling systemDirect seawater cooling by rubber impeller seawater pump
Lubrication system Enclosed, forced lubricating system
Direction of rotation [crankshaft]Counterclockwise viewed from flywheel side
Dry weight with gear76 kg
168 lbs

TOP TIP: Use this handy printout to record all the important details about your Yanmar engine and then file it away safely at home for future reference.

Upgrade jobs for your Yanmar 1GM

Maintenance jobs for your Yanmar 1GM

  • Changing the primary fuel filter on your marine diesel installation
  • Checking and tensioning the alternator drive belt on your Yanmar 1GM
  • Removal and inspection of the air filter on the 1GM
  • Removal and inspection of the exhaust mixing elbow on the 1GM
  • Changing the gearbox oil
  • Descaling the raw-water coolant channels in your 1GM

Winterising jobs for your Yanmar 1GM

Before haul-out:

  • Yanmar 1GM engine oil and filter change

After haul-out:

  • Flushing salt-water from the Yanmar 1GM and introducing anti-freeze
  • Clean and winterise the raw-water filter

Before launch:

After launch:

Video Clip: Click to watch a video of a Yanmar 1GM running

A smart skipper learns from the lessons of others.

In our Yanmar GM Series Almanac section, we have a series of previous questions and queries from Yanmar GM owners along with answers. Many of these have been adapted from discussions on the “Yanmar Marine Engine Owner’s Group – Repair and Discussion” Facebook group which is a fantastic resource for getting help.

Do you want to get future Yanmar GM Series Almanac articles straight to your inbox? Sign up to our Yanmar GM Series Owners’ Group today and we’ll make sure that you’re first to see them. And we definitely won’t share your email address with anyone else.