________________________________________________________________________________

Yanmar 2V78C Engine

The Yanmar 2V78C is a heavy-duty, industrial-grade liquid-cooled, vertical V-twin, four-stroke diesel engine designed for compact utility and industrial machinery. Engineered to reduce noise and structural vibration, it provides a smoother operational profile comparable to three-cylinder configurations while maintaining a high power-to-weight ratio. It features a vertical cylinder configuration with indirect injection for cleaner, more reliable combustion under varied loads.

Valves per Cylinder: 2 valves (1 intake, 1 exhaust) actuated via a traditional pushrod overhead valve (OHV) mechanism driven by a single gear-driven camshaft. Cylinder Bore: 78 mm (3.07 in). Piston Stroke: 78.4 mm (3.09 in). Total Displacement: 749 cc (45.7 cu. in.). Lubrication System: Fully pressurized force-feed lubrication system. Oil Pump Type: Trochoid pump driven by the crankshaft gear train. Filtration: Full-flow replaceable spin-on oil filter cartridge alongside an integrated oil pressure safety switch.

Fuel System: Indirect Injection (IDI) design utilizing specialized pre-combustion chambers to optimize fuel atomization and lower emission levels. Injection Pump: Mechanical Yanmar inline fuel injection pump calibrated to respond quickly to sudden mechanical loads via a centrifugal all-speed mechanical governor. Fuel Delivery and Safety: Employs dual-stage high-pressure fuel injection valves (nozzles), a mechanical fuel priming/feed pump, a water separator/fuel filter assembly, and an electrical stop solenoid for instant emergency engine shutdowns.

Cooling System: Liquid-cooled with a closed-loop force-feed circulation system. Circulation Mechanism: Belt-driven centrifugal water pump working in conjunction with a multi-blade suction cooling fan. Thermal Regulation: Controlled via a wax-pellet type thermostat and protected by a built-in water temperature switch.

General Technical Data

Engine Specifications

Engine Model ............... Yanmar 2V78C
Engine Type ............... 4-cycle vertical V-twin liquid-cooled diesel
Number of Cylinders ............... 2
Cylinder Arrangement ............... V-twin 90-degree configuration
Engine Bore, in (mm) ............... 3.07 (78.0)
Engine Stroke, in (mm) ............... 3.09 (78.4)
Displacement, cu.in (L) ............... 45.7 (0.749)
Rated Power, hp (kW) ............... 18.0-18.8 (13.4-14.0) at 3000 rpm
Rated Speed, rpm ............... 3000
Maximum No-Load Speed, rpm ............... 3200-3250
Minimum Low Idle Speed, rpm ............... 2400-2475
Peak Torque ............... 28.0 lb-ft (37.6 Nm) at 2250 rpm
Aspiration Type ............... Naturally aspirated
Compression Ratio ............... 23.0:1-24.0:1
Firing Order ............... 1-2
Combustion Chamber ............... Indirect injection swirl pre-combustion chamber
Direction of Rotation ............... Counter-clockwise facing the flywheel side
Cylinder Block Type ............... Cast iron deep-skirt design
Cylinder Head Type ............... Cast iron overhead valve design
Lubrication System ............... Full forced pressure lubrication via trochoid pump
Oil Pump Type ............... Gear-driven trochoid rotary type
Oil Filter Type ............... Full-flow spin-on cartridge type
Cooling System ............... Liquid-cooled with radiator and expansion reservoir
Water Pump Type ............... Belt-driven centrifugal impeller type
Air Cleaner Type ............... Dry dual-element replaceable paper with cyclonic housing
Starting System ............... Electric motor starter
Electrical System ............... 12V negative ground system
Alternator Capacity ............... 40A or 60A depending on production variant

Fuel System

Fuel Injection Pump Type ............... Yanmar inline YPD mini pump type
Fuel Injection Nozzle Type ............... Throttle type nozzle orifice
Fuel Injection Pressure, psi (MPa) ............... 1707-1849 (11.8-12.7)
Fuel Transfer Pump Type ............... Mechanical diaphragm type or electric pulse type
Fuel Filter Type ............... Spin-on element with water separator bowl
Fuel Delivery Lines ............... High-pressure seamless steel piping with anti-vibration clamps
Fuel Injection Timing, deg ............... 14-16 before top dead center
Maximum Fuel Return Flow, gal/hr (L/hr) ............... 1.3-2.1 (5.0-8.0)
Governor Type ............... Mechanical centrifugal all-speed governor
Governor Linkage Type ............... Internal mechanical control rack with tension spring control
Fuel Feed Line Inner Diameter, in (mm) ............... 0.23 (6.0)
Fuel Return Line Inner Diameter, in (mm) ............... 0.19 (4.8)
Maximum Fuel Pump Inlet Suction, inHg (mmHg) ............... 3.93 (100.0)
Maximum Permissible Fuel Temperature, F (C) ............... 122 (50.0)
Fuel Tank Vent Air Flow Minimum, cfm (L/min) ............... 0.70 (20.0)

Dimensions and Weight

Engine Length, in (mm) ............... 17.2 (435)
Engine Width, in (mm) ............... 18.5 (470)
Engine Height, in (mm) ............... 20.3 (515)
Dry Engine Weight, lbs (kg) ............... 155 (70)
Wet Engine Weight, lbs (kg) ............... 165 (75)

Maintenance Data

Service Information

Minimum Compression Pressure, psi (MPa) ............... 426 (2.94)
Standard Compression Pressure, psi (MPa) ............... 497 (3.43)
Oil Pressure at Rated Speed, psi (MPa) ............... 42.6-56.8 (0.29-0.39)
Oil Pressure at Idle Speed, psi (MPa) ............... 14.2 (0.10)
Oil Temperature Standard Range, F (C) ............... 185-221 (85.0-105.0)
Standard Coolant Operating Temperature, F (C) ............... 167-194 (75.0-90.0)
Thermostat Valve Opening Temperature, F (C) ............... 160 (71.0)
Thermostat Full Open Temperature, F (C) ............... 185 (85.0)
Intake Valve Clearance (Cold), in (mm) ............... 0.0059-0.0078 (0.150-0.200)
Exhaust Valve Clearance (Cold), in (mm) ............... 0.0059-0.0078 (0.150-0.200)

Engine Oil and Coolant

Engine Oil Type .................. SAE 30, SAE 10W-30, or SAE 15W-40
API Service Classifications ......................... CD or higher
Engine Oil Capacity with Filter, qt (L) ............... 2.32 (2.2)
Engine Oil Capacity without Filter, qt (L) ............... 2.11 (2.0)
Cooling System Capacity, qt (L) ............... 1.58 (1.5)

Service Intervals

Change oil and filter ............... Every 200 hours
Inspect air cleaner ............... Every 50 hours
Replace air cleaner ............... Every 250 hours
Replace fuel filter ............... Every 200 hours
Valve clearance adjustment ............... Every 500 hours
Fuel system inspection ............... Every 1000 hours
Change coolant ............... Every 1000 hours
Compression test ............... Every 1000 hours
Clean radiator core ............... Every 200 hours
Inspect belt tension ............... Every 100 hours

Service Specifications

Cylinder Bore Inside Diameter, in (mm) ............... 3.0708-3.0712 (78.000-78.010)
Cylinder Bore Wear Limit Maximum, in (mm) ............... 3.0787 (78.200)
Cylinder Bore Out-of-Round Limit, in (mm) ............... 0.0004 (0.010)
Cylinder Block Upper Deck Surface Warpage Flatness, in (mm) ............... 0.0019 (0.050)
Main Bearing Journal Bore I.D, in (mm) ............... 1.8897-1.8903 (48.000-48.016)
Connecting Rod Small End Bushing I.D, in (mm) ............... 0.8665-0.8673 (22.010-22.030)
Connecting Rod Big End I.D, in (mm) ............... 1.6929-1.6933 (43.000-43.010)
Crankpin Standard Diameter, in (mm) ............... 1.5744-1.5748 (39.991-40.000)
Crankpin Bearing Clearance, in (mm) ............... 0.0011-0.0025 (0.030-0.064)
Connecting Rod Bearing Clearance, in (mm) ............... 0.0047 (0.120)
Connecting Rod Side Play, in (mm) ............... 0.0059-0.0137 (0.150-0.350)
Crankshaft Main Journal Diameter, in (mm) ............... 1.7318-1.7322 (43.991-44.000)
Crankshaft Main Bearing Clearance, in (mm) ............... 0.0011-0.0026 (0.030-0.068)
Crankshaft End Play, in (mm) ............... 0.0043-0.0082 (0.110-0.210)
Piston Skirt Outside Diameter, in (mm) ............... 3.0681-3.0689 (77.930-77.950)
Piston to Cylinder Wall Clearance, in (mm) ............... 0.0019-0.0031 (0.050-0.080)
Piston Pin Bore Inside Diameter, in (mm) ............... 0.8661-0.8665 (22.000-22.009)
Piston Pin Outside Diameter, in (mm) ............... 0.8657-0.8661 (21.989-22.000)
Piston Pin to Piston Pin Bore Clearance , in (mm) ............... 0.0000-0.0007 (0.000-0.020)
Top Ring Groove Width, in (mm) ............... 0.0602-0.0610 (1.530-1.550)
Second Ring Groove Width, in (mm) ............... 0.0602-0.0610 (1.530-1.550)
Oil Ring Groove Width, in (mm) ............... 0.1185-0.1193 (3.010-3.030)
Top Ring Side Clearance, in (mm) ............... 0.0024-0.0039 (0.060-0.100)
Second Ring Side Clearance, in (mm) ............... 0.0019-0.0035 (0.050-0.090)
Oil Ring Side Clearance, in (mm) ............... 0.0012-0.0028 (0.030-0.070)
Top Ring End Gap, in (mm) ............... 0.0059-0.0118 (0.150-0.300)
Second Ring End Gap, in (mm) ............... 0.0059-0.0118 (0.150-0.300)
Oil Ring End Gap, in (mm) ............... 0.0078-0.0157 (0.200-0.400)
Cylinder Head Bottom Surface Distortion Flatness, in (mm) ............... 0.0011 (0.030)
Intake Valve Stem Outside Diameter, in (mm) ............... 0.2346-0.2350 (5.960-5.970)
Exhaust Valve Stem Outside Diameter, in (mm) ............... 0.2340-0.2344 (5.945-5.955)
Intake Valve Guide Inside Diameter, in (mm) ............... 0.2362-0.2367 (6.000-6.012)
Exhaust Valve Guide Inside Diameter, in (mm) ............... 0.2362-0.2367 (6.000-6.012)
Intake Valve Stem-to-Guide Clearance, in (mm) ............... 0.0011-0.0020 (0.030-0.052)
Exhaust Valve Stem-to-Guide Clearance, in (mm) ............... 0.0017-0.0026 (0.045-0.067)
Intake Valve Seat Angle, deg ............... 45
Exhaust Valve Seat Angle, deg ............... 45
Intake Valve Face Angle, deg ............... 45
Exhaust Valve Face Angle, deg ............... 45
Intake Valve Sink Depth, in (mm) ............... 0.0157-0.0236 (0.400-0.600)
Exhaust Valve Sink Depth , in (mm) ............... 0.0157-0.0236 (0.400-0.600)
Valve Spring Free Length, in (mm) ............... 1.3937 (35.400)
Camshaft Main Journal Diameter, in (mm) ............... 1.4169-1.4173 (35.991-36.000)
Camshaft Journal Bearing Clearance, in (mm) ............... 0.0011-0.0029 (0.030-0.075)
Camshaft Cam Lobe Height (Intake), in (mm) ............... 1.2582-1.2614 (31.960-32.040)
Camshaft Cam Lobe Height (Exhaust), in (mm) ............... 1.2582-1.2614 (31.960-32.040)
Rocker Arm Shaft Outside Diameter, in (mm) ............... 0.4716-0.4720 (11.980-11.990)
Rocker Arm Bushing Inside Diameter, in (mm) ............... 0.4724-0.4732 (12.000-12.020)
Rocker Arm Shaft-to-Bushing Clearance, in (mm) ............... 0.0003-0.0015 (0.010-0.040)
Crankshaft Timing Gear to Camshaft Gear Backlash, in (mm) ............... 0.0027-0.0055 (0.070-0.140)
Camshaft Gear to Idler Gear Backlash, in (mm) ............... 0.0027-0.0055 (0.070-0.140)
Idler Gear to Oil Pump Gear Backlash, in (mm) ............... 0.0027-0.0055 (0.070-0.140)
Idler Gear to Oil Pump Gear Backlash, in (mm) ............... 0.0098 (0.250)

Tightening Torques

Cylinder Head Bolt, lb-ft (Nm) ............... 39.1-43.4 (53.0-59.0)
Connecting Rod Cap Bolt, lb-ft (Nm) ............... 17.4-20.2 (23.5-27.5)
Main Bearing Cap Bolt, lb-ft (Nm) ............... 39.1-43.4 (53.0-59.0)
Flywheel Mounting Bolt, lb-ft (Nm) ............... 57.8-65.1 (78.4-88.3)
Flywheel Housing Cap Screw, lb-ft (Nm) ............... 17.4-21.7 (23.5-29.4)
Crankshaft Pulley End Bolt, lb-ft (Nm) ............... 61.4-69.4 (83.3-94.1)
Camshaft Thrust Plate Bolt, lb-ft (Nm) ............... 6.5-8.7 (8.8-11.8)
Rocker Arm Shaft Support Bracket Bolt, lb-ft (Nm) ............... 6.5-8.7 (8.8-11.8)
Valve Cover Bonnet Bolt, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Oil Pan Drain Plug, lb-ft (Nm) ............... 21.7-28.9 (29.4-39.2)
Oil Pan Mounting Bolt, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Gear Case Front Cover Bolt, lb-ft (Nm) ............... 6.5-8.7 (8.8-11.8)
Gear Case Front Cover Bolt, lb-ft (Nm) ............... 17.4-21.7 (23.5-29.4)
Fuel Injection Pump Retaining Nut, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Fuel Injection Pump Delivery Valve Holder, lb-ft (Nm) ............... 25.3-28.9 (34.3-39.2)
Fuel Injection Nozzle Case Nut, lb-ft (Nm) ............... 28.9-36.1 (39.2-49.0)
Fuel Injection Nozzle Holder Bolt, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Fuel Injection Nozzle Holder Joint Nut, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Fuel Return Line Joint Bolt, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Fuel Pump Spill Timing Hole Plug, lb-ft (Nm) ............... 7.2-10.8 (9.8-14.7)
Exhaust Manifold Mounting Stud Nut, lb-ft (Nm) ............... 17.4-21.7 (23.5-29.4)
Intake Manifold Mounting Bolt, lb-ft (Nm) ............... 6.5-8.7 (8.8-11.8)
Starter Motor Mounting Bolt, lb-ft (Nm) ............... 17.4-21.7 (23.5-29.4)
Alternator Pivot Mount Bolt, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Alternator Adjuster Link Tensioning Bolt, lb-ft (Nm) ............... 6.5-8.7 (8.8-11.8)
Oil Pressure Switch, lb-ft (Nm) ............... 7.2-10.8 (9.8-14.7)
Coolant Temperature Switch, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)
Glow Plug Torque, lb-ft (Nm) ............... 5.8-8.7 (7.8-11.8)
Water Pump Assembly Mounting Bolt, lb-ft (Nm) ............... 6.5-8.7 (8.8-11.8)
Thermostat Housing Cover Bolt, lb-ft (Nm) ............... 6.5-8.7 (8.8-11.8)
Radiator Fan Mounting Bolt, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Oil Pump Stator Base Cover Screw, lb-ft (Nm) ............... 4.3-6.5 (5.9-8.8)
Idler Shaft Plate Bolt, lb-ft (Nm) ............... 6.5-8.7 (8.8-11.8)
Oil Pressure Relief Valve Plug, lb-ft (Nm) ............... 17.4-23.1 (23.5-31.4)
Fuel Filter Bracket Wall Bolt, lb-ft (Nm) ............... 17.4-21.7 (23.5-29.4)
Air Cleaner Bracket Clamping Screw, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Muffler Flange Attachment Stud Nut, lb-ft (Nm) ............... 17.4-21.7 (23.5-29.4)
Stop Solenoid Lock Nut, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)

________________________________________________________________________________________

• Yanmar Engines Specs
  
• Yanmar 2V750 Specs
  
• Yanmar 2V78 Specs
  
• Yanmar 3D82AE Specs
  
• Yanmar 3D84 Specs
  

________________________________________________________________________________

________________________________________________________________________________________

_______________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________