John Deere 6068SFM85 Specifications
| Engine Model: John Deere PowerTech 6068SFM85 |
| Engine Type: 4-stroke in-line 6-cylinder turbocharged liquid-cooled diesel |
| Total Displacement: 415 cu.in (6.8 L) |
| Rated Engine Power: 249-400 Hp (186-298 kW) at 2400-2800 rpm |
| Fuel System Type: Common Rail Direct Injection |
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The John Deere 6068SFM85 is a 6.8-liter,
6-cylinder marine diesel engine from the PowerTech series. This power
unit is engineered for high-performance propulsion and constant-speed
auxiliary applications in commercial and recreational vessels. The
engine complies with EPA Marine Tier 3 and IMO Tier II emission
standards through a high-pressure common rail (HPCR) fuel system and
electronic engine control. The SFM85 designation indicates a
turbocharged configuration with air-to-seawater aftercooling, a wet
exhaust manifold, and a high-capacity heat exchanger.
Five power ratings, designated M1 through M5, match the engine to
specific duty cycles ranging from unrestricted continuous operation to
recreational high-performance use. The replaceable wet-type cylinder
liners and water-cooled exhaust manifold contribute to serviceability
and reduced engine room temperatures. This engine replaces earlier
mechanically governed marine versions of the 6.8L platform.
Engine Type: In-line, 4-cycle diesel, turbocharged, air-to-seawater
aftercooled.
Number of Cylinders: 6.
Displacement: 6.8 L (415 cu.in).
Bore x Stroke: 106 mm x 127 mm (4.17 in x 5.00 in).
Compression Ratio: 16.3:1.
Aspiration: Turbocharged with air-to-seawater aftercooler.
Cylinder Liners: Replaceable wet-type.
Firing Order: 1-5-3-6-2-4.
Rotation (from flywheel end): Counter-clockwise standard. Clockwise
optional.
Rated Power M1 (Unrestricted Continuous): 186 kW (249 hp) at 2400 rpm.
Rated Power M2 (Short-range / 16 hr per 24 hr): 209 kW (280 hp) at 2500
rpm.
Rated Power M3 (Performance / 4 hr per 12 hr): 239 kW (321 hp) at 2600
rpm.
Rated Power M4 (High Performance / 1 hr per 12 hr): 265 kW (355 hp) at
2700 rpm.
Rated Power M5 (Recreational Only / 0.5 hr per 8 hr): 298 kW (400 hp) at
2800 rpm.
Peak Torque (M5 rating): 1230 Nm (907 lb-ft) at 2200 rpm.
Low Idle Speed: 750-800 rpm.
High Idle Speed (no-load, M5): 2950 rpm.
Emission Standard: EPA Marine Tier 3, IMO Tier II.
0The cylinder block is manufactured from high-strength cast iron with a
deep-skirt design extending below the crankshaft centerline. Seven main
bearing bulkheads provide crankshaft support. The block incorporates
replaceable wet-type cylinder liners, each sealed at the lower bore by
two elastomeric O-rings and at the upper flange by a pressed-in copper
fire ring. Liners are centrifugally cast from alloy iron with a hardened
internal bore finish.
Cross-bolted main bearing caps are fitted to the center three positions
for increased rigidity under high cylinder pressures generated by the
common rail system. The water jacket surrounds each liner fully,
permitting direct seawater-cooled coolant contact. Cast oil galleries
run the entire block length, supplying the main bearings, connecting
rods, and piston cooling jets. A rear gear train housing is integrated
into the block casting for accessory drives.
The cylinder head is a single-piece cast iron component with a
cross-flow intake and exhaust arrangement. The intake ports are located
on the starboard side, and exhaust ports on the port side for marine
installations. Each cylinder receives four valves: two intake and two
exhaust, arranged in a parallel configuration. The valvetrain is an
overhead valve (OHV) design with pushrods, roller followers, and rocker
arms.
Valve stem seals are positive-type on all valves. Hardened sintered
valve seat inserts resist wear and corrosion from marine exhaust gases.
The cylinder head incorporates an integrated exhaust passage that routes
gases to a water-cooled exhaust manifold. Valve rotators are installed
on exhaust valves to prevent carbon buildup and extend service life.
Hydraulic lash adjusters eliminate routine valve clearance maintenance.
Glow plugs are installed in each intake port for cold start assistance.
The fuel system is a high-pressure common rail (HPCR) design with full
electronic engine control. A gear-type transfer pump draws fuel from the
marine fuel tank and delivers it at 5-7 bar (73-102 psi) to a
high-pressure pump. The high-pressure pump, a radial piston design with
three pumping elements, generates rail pressure up to 1600 bar (23,200
psi). The common rail accumulator distributes pressurized fuel to six
electronically controlled solenoid injectors.
An engine control unit (ECU) governs injection timing, duration, and
pressure based on sensors monitoring crankshaft position, camshaft
position, boost pressure, coolant temperature, and fuel rail pressure.
Each injection event may include up to five separate discharges per
combustion cycle: pilot, main, and post injections. The ECU also manages
engine speed governing, torque limiting, and emission control functions.
A seawater-cooled fuel cooler prevents vapor lock in the high-pressure
system.
The lubrication system uses a gear-type oil pump mounted on the front
timing gear case. The pump draws oil through a suction strainer
positioned in the deep marine oil sump. Oil passes through a full-flow
spin-on filter with a bypass valve set at 2.1 bar (30 psi). A
water-cooled oil cooler, utilizing seawater on the tube side and engine
oil on the shell side, regulates oil temperature. The system
incorporates six piston cooling jets, one per cylinder, threaded into
the main oil gallery.
Each jet directs a continuous spray toward the underside of the piston
crown. An oil pressure relief valve opens at 5.5 bar (80 psi). The
marine oil sump capacity, including filter, is 22.0 L (23.2 qt) for the
standard forward sump and 24.0 L (25.4 qt) for the rear sump
configuration. Oil pressure at rated speed measures 3.4-4.8 bar (50-70
psi). A low oil pressure switch triggers an audible alarm at 0.7 bar (10
psi).0
The cooling system comprises two separate circuits: a high-temperature
fresh water circuit and a low-temperature seawater circuit. The fresh
water circuit cools the engine block, cylinder head, and exhaust
manifold. A belt-driven centrifugal water pump circulates coolant
through the engine. The wax-pellet thermostat begins opening at 82°C
(180°F) and reaches full opening at 95°C (203°F). The seawater circuit,
driven by a rubber-impeller pump, draws raw water through a hull
strainer.
Seawater passes through the gear-driven aftercooler, then through the
oil cooler, next through the heat exchanger, and finally discharges
through the wet exhaust elbow. The heat exchanger is a shell-and-tube
design with corrosion-resistant cupronickel tubes. Coolant capacity for
the engine fresh water circuit is 13.5 L (14.3 qt). Total seawater flow
at rated speed is 150 L/min (40 gal/min). A seawater pressure switch
activates a warning alarm if flow drops below 0.7 bar (10 psi) at the
pump outlet.
Aspiration: Fixed-geometry turbocharger with a seawater-cooled bearing
housing. The turbocharger is mounted on a water-cooled exhaust manifold.
Boost pressure at rated power reaches 1.4 bar (20.3 psi).
Aftercooler: Air-to-seawater plate-type aftercooler mounted between the
turbocharger compressor outlet and intake manifold. Aftercooler reduces
intake air temperature from 150°C (302°F) to 48°C (118°F) at full load.
Exhaust System: Water-cooled cast iron exhaust manifold integrated with
a wet elbow. Seawater injects into the exhaust stream at the elbow,
reducing exhaust gas temperature from 550°C (1022°F) to below 60°C
(140°F) at the discharge point. The manifold incorporates a condensate
drain.
Electrical System: 24 volt negative ground standard. 12 volt optional
for recreational applications. Starter motor rating is 6.0 kW.
Alternator output is 120 A with a seawater-cooled regulator. ECU
operates at 5 V and 12 V internal supply levels.
Engine Control Unit (ECU): Bosch EDC17 mounted directly on the engine.
The Ecu.integrates a marine-specific governor with both droop and
isochronous modes selectable via vessel control panel. A diagnostic port
supports J1939 CAN bus communication.
Governor: Electronic governor integral to the ECU. Governing accuracy
for generator applications is ±0.25% at constant load. For propulsion,
the governor provides a 5-10% droop characteristic.
Length (maximum, flywheel housing to front pulley): 1489 mm (58.6 in)
Width (maximum, exhaust manifold to alternator): 872 mm (34.3 in)
Height (oil pan rail to rocker cover peak): 931 mm (36.7 in)
Dry Weight (engine only, no gearbox): 763 kg (1682 lb)
Dry Weight (with standard marine gearbox, SAE #1): 980 kg (2160 lb)
Oil Pan to Crankshaft Center Distance (forward sump): 175 mm (6.9 in)
Engine Oil Change Interval: 500 hours or 12 months under normal marine
duty.
Engine Oil Capacity (standard forward sump, including filter): 22.0 L
(23.2 qt)
Engine Oil Capacity (rear sump, including filter): 24.0 L (25.4 qt)
Engine Oil Grade (ambient above 0°C / 32°F): SAE 15W-40, API CJ-4 or
higher.
Engine Oil Grade (cold ambient): SAE 5W-40 or SAE 10W-30, API CJ-4.
Engine Oil Pressure at Rated Speed: 3.4-4.8 bar (50-70 psi)
Engine Oil Pressure at Low Idle (minimum, warm engine): 0.7 bar (10 psi)
Coolant Capacity (fresh water circuit, engine only): 13.5 L (14.3 qt)
Coolant Capacity (fresh water circuit, system total): 28.0-32.0 L
(29.6-33.8 qt).
Coolant Specification: Ethylene glycol base, heavy-duty marine
formulation.
Seawater Pump Impeller Replacement Interval: 500 hours or 12 months.
Heat Exchanger Tube Cleaning Interval: 1000 hours or annually.
Thermostat Opening Temperature: 82°C (180°F) start; fully open at 95°C
(203°F).
Fuel Filter Replacement Interval (primary and secondary): 500 hours.
Air Filter Service Interval: Replace when restriction indicator reaches
6.2 kPa (25 in water).
Injector Replacement Interval: 3000 hours or as indicated by cylinder
balance testing.
Turbocharger Inspection Interval: 2000 hours. Check for shaft end play
(max 0.20 mm / 0.008 in).
Aftercooler Cleaning Interval: 1000 hours.
Drive Belt (serpentine) Replacement Interval: 1000 hours.
Cylinder Liner Protrusion: 0.05-0.13 mm (0.002-0.005 in) measured above
the block deck.
Engine Zinc Anode Replacement: 250 hours or 6 months in saltwater
operation.
Cylinder Head Bolts (Stage 1): 100 Nm (74 lb-ft)
Cylinder Head Bolts (Stage 2): 150 Nm (111 lb-ft)
Connecting Rod Cap Bolts: 58 Nm (43 lb-ft)
Main Bearing Cap Bolts (inner, all caps): 135 Nm (100 lb-ft)
Main Bearing Cap Cross Bolts (center three caps): 80 Nm (59 lb-ft)
Flywheel Bolts (to crankshaft flange): 130 Nm (96 lb-ft)
Flywheel Housing Bolts (to block): 90 Nm (66 lb-ft)
Camshaft Thrust Plate Bolts: 30 Nm (22 lb-ft)
Rocker Arm Shaft Pedestal Bolts: 45 Nm (33 lb-ft)
Rocker Cover Bolts (rubber gasket): 12 Nm (9 lb-ft)
High-Pressure Pump Mounting Bolts: 25 Nm (18 lb-ft)
Common Rail Mounting Bolts: 22 Nm (16 lb-ft)
Injector Clamp Bolts: 28 Nm (21 lb-ft)
High-Pressure Fuel Line Nuts: 35 Nm (26 lb-ft)
Crankshaft Pulley Bolts: 90 Nm (66 lb-ft)
Viscous Damper Center Bolt: 450 Nm (332 lb-ft)
Oil Pan Bolts (M10): 35 Nm (26 lb-ft)
Oil Pan Drain Plug (magnetic): 50 Nm (37 lb-ft)
Oil Cooler Mounting Bolts (to block): 40 Nm (30 lb-ft)
Seawater Pump Mounting Bolts: 25 Nm (18 lb-ft)
Seawater Pump Cover Bolts (impeller access): 12 Nm (9 lb-ft)
Water Pump (fresh water) Mounting Bolts: 40 Nm (30 lb-ft)
Thermostat Housing Bolts: 25 Nm (18 lb-ft)
Heat Exchanger Mounting Bolts: 45 Nm (33 lb-ft)
Aftercooler Mounting Bolts: 25 Nm (18 lb-ft)
Starter Motor Mounting Bolts (24V, SAE #1): 70 Nm (52 lb-ft)
Alternator Bracket Bolts (stainless steel): 45 Nm (33 lb-ft)
Turbocharger Mounting Nuts (to manifold): 60 Nm (44 lb-ft)
Turbocharger Oil Supply Line Fitting: 25 Nm (18 lb-ft)
Turbocharger Seawater Cooling Line Fittings: 20 Nm (15 lb-ft)
Exhaust Manifold Water Jacket Bolts: 35 Nm (26 lb-ft)
Flex Plate to Flywheel Bolts (if equipped): 60 Nm (44 lb-ft)
Engine Mount Bracket Bolts (isolation mounts): 100 Nm (74 lb-ft)
Commercial Vessels (M1 and M2 ratings): Workboats up to 20 m (65 ft)
length. Crew boats, pilot boats, and patrol vessels requiring continuous
operation. Trawlers and long-range cruising yachts with displacement
hulls.
Recreational Vessels (M3, M4, M5 ratings): Planing motor yachts from 12
m (40 ft) to 24 m (80 ft). Sportsfisher vessels and express cruisers.
Catamarans and fast trawlers. Applications include single-engine and
twin-engine propulsion configurations.
Auxiliary Power (M1 rating constant speed): Marine generator sets at
1500 rpm (50 Hz) or 1800 rpm (60 Hz) for auxiliary power on large yachts
and commercial ships. Hydraulic power packs for bow thrusters and deck
equipment.
Coast Guard and Law Enforcement (M2 rating): Interceptor vessels and
response boats. Search and rescue craft.
Fireboats and Tenders (M1 and M2): Harbor fireboats, ship tenders, and
utility launches. Deck drain cooling systems integrated for idle
operation.
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