Yanmar 1GM - Service Manual
Chapter 1 - BASIC ENGINE

1. Exterior Views

1GM - Intake side viewed from stern / port side		1GM - Exhaust side viewed from bow / stbd side

2. Specifications

3. Principal Construction

4. Performance Curves

1GM - Performance Curves		1GM10 - Torque		1GM10 - Fuel Consumption				1GM10 - Power Out

5. Features

5-1 Superior combustion performance

The unique Yanmar swirl precombustion chamber and new cooling system display superior combustion performance in all types of operation. Low-speed, low-load combustion performance, especially demanded for marine applications, is also superb, and stable performance is maintained over a wide range of speeds. Since starting characteristics are also excellent and warm-up speed is fast, full engine performance can be obtained within a short time.

5-2 Low operating costs

Excellent combustion and low friction reduce fuel costs, while the optimized piston shape and ring configuration and improved cooling system reduce oil consumption. Continuous operating time have been extended and operating costs reduced throughout improved durability.

5-3 Compact, lightweight

The cylinder head is the integrally-cast type, and the crankshaft is the housing type. Minimum weight has been pursued for each engine part, and a reduction revering gear employing a special new mechanism has been incorporated to obtain revolutionary engine lightness.

5-4 Long term continuous operation

Improved durability has been achieved by adopting special construction and materials for main moving paths and the valve mechanism, which are the areas most subject to trouble in high-speed engines. Moreover, a bypass system with a thermostat maintains the cooling water at a table high temperature, resulting in reduced cylinder liner and piston ring wear, reduced thermal load around the combustion chamber, and substantially improved durability. Long-term continuous operation is possible by correct operation and proper attention to fuel and lubricating oil.

5-5 Low vibration

Vibration has been reduced by minimizing the weights of the pistons, connecting rods, and other sources of vibration, stringent weight management at assembly, and balancing of the flywheel, V-pulley, etc. Vibration has also been suppressed through the adoption of a special cylinder block rib construction and improved rigidity. Rubber shock mounts are available when the engine is to be used which may lead to severe vibration.

5-6 Quiet operation

Intake and exhaust noises have been lowered by adopting an intake silencer, water-cooled exhaust manifold, and water mixing elbow type exhaust system.

The precombustion chamber system and semi-throttle type injection valve suppress combustion noise substantially.

Moreover, gear noise has been reduced by the use of helical gears around the gear train and clutch gear, and by the buffering effect of a damper disc.

In addition, noise prevention measures have also been taken at the control valve mechanism and other parts.

5-7 Superior matching to the hull

(1) Four-point support engine installation feet make installation easy.
(2) Mist intake system prevents contamination of the engine room.
(3) Since the fuel pump is mounted on the engine, the fuel tank can be installed anywhere.
(4) Water-cooled manifold prevents a rise in the engine room temperature.
(5) Independent type instrument panel can be installed wherever it is easiest to see.
(6) Speed, clutch forward and reverse, and engine stop can all be remotely controlled.
(7) The use of rubber and vinyl hoses for ship interior piping not only facilitates piping work, but also eliminates brazing faults caused by vibration.
(8) Electric type bilge pump is available as an option.

5-8 Easy to operate

(1) Cooling water temperature switch and lubricating oil pressure switch are provided, and alarm lamps and buzzer are mounted on the instrument panel.
(2) Manual starting handle permits manual starting.
(3) Positive clutch engagement and disengagement; propeller shaft does not rotate when clutch is placed in neutral position.

6. Engine Cross-Section

1GM - Engine Cross-Section - front		1GM - Engine Cross-Section - side

7. Dimensions

1GM - Plan View		1GM - Body (stern) View		1GM - Profile View		1GM - Body (bow) View
1GM10 - Profile		1GM10 - Back		1GM10 - Top		Shaft Coupling

8. Piping Diagram

1GM Piping Diagram

9. System Diagrams

1GM Cooling System		1GM Lubrication System		1GM Fuel System		1GM Electrical System

10. Standard Accessories

10-1 Parts packed with engine

The parts packed with the listed below.

10-2 Parts mounted on engine

The parts mounted on the engine are listed below.

11. Optional Accessories

11-1 Parts mounted on engine

The parts mounted on the engine are listed below.

11-2 Parts packed with the engine

The parts mounted on the engine are listed below.