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.
| Model | 1GM | 1GM10 |
|---|---|---|
| Idle (no-load) speed (rpm) | 850 | 850 |
| Full load speed (rpm) | 3750 | 3825 |
| Fuel Injection Timing | 25° before TDC | 15° before TDC |
| Valve Clearance | 0.2 m (0.008 in.) | 0.2 m (0.008 in.) |
| Oil Capacity | 1.3 litres / 1.4 qt | 1.3 litres / 1.4 qt |
| Num of Cylinders | 1 | 1 |
| Displacement | 293 cc / 17.9 cu. in. | 318 cc / 19.4 cu. in. |
| Horsepower | 6.5 hp @ 3400 rpm | 8 hp @ 3400 rpm |
| Gearbox | KM2A | KM2C or KM2P |
| Gearbox Ratio | 2.21, 2.62 or 3.22 | 2.21, 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
- Nameplate
- Thermostat cover
- Fuel injection pump
- Idle adjustment
- Oil filler cap
- Fuel injection limiter
- Engine stop level
- Crankshaft V-pulley
- Seawater pump
- Oil filter
- Regulator handle
- Fuel lift pump
- Dipstick
- Mounting flange
- Mixing elbow
- Fuel filter
Components of the Yanmar 1GM – port side
- Decompression lever
- Fuel injection valve
- Intake silencer
- Tachometer sensor
- Marine gear dipstick
- Marine gearbox
- Output shaft coupling
- Shift lever
- Starter motor
- Alternator
Specifications of the Yanmar 1GM10 Marine Diesel Engine
| Feature | Yanmar 1GM10 |
|---|---|
| Configuration | 4-stroke, vertical, raw water-cooled diesel engine |
| Maximum output at crankshaft | 6.7 kW@3600 rpm 9 mhp@3600 rpm at a fuel temperature of 25° C. |
| Displacement | 0.318 litres 19.41 cu. in. |
| Bore x stroke | 75 mm x 72 mm 2.95 in x 2.83 in |
| Cylinders | 1 |
| Combustion system | Indirect injection [special swirl type pre-combustion chamber] |
| Aspiration | Natural |
| Starting system | Electric starting 12V - 1.0 kW with manual combination |
| Alternator | 12V – 40A |
| Cooling system | Direct 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 gear | 76 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
- Adding a hour meter to your Yanmar GM series engine
- Adding a relay to the starter circuit to fix intermittant starting issue
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:
- Stern gear: Grease your lip seal or refill the greaser on your stuffing box
- Changing the secondary fuel filter on the Yanmar 1GM
- Changing the water-pump impeller on your Yanmar 1GM
- Removal and inspection of the raw-water anode on your Yanmar 1GM
- Removing and testing the thermostat on your Yanmar 1GM
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.
- White Smoke & Black Water from a Yanmar 2GM20
- KM2P Transmission Oil level question – please can someone help?
- Yanmar 1GM won’t go over 2700 RPM
- This Yanmar 2GM20 only started with one decompression lever engaged
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