John Deere
6068TFM50
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John Deere 6068TFM50 John Deere 6068TFM50
You'll find John Deere diesels aboard commercial and fishing vessels the world over, so if you are considering re-powering you should definitely look into this brand. Deere's PowerTech 6068 series comprises models from 158- to 400-hp, in both heat-exchanged and keel-cooled version. FYI -- the last five years or so they have become very popular among builders of trawlers and long range cruisers, so John Deere must be doing something right.

Key Features

  • Watercooled Turbocharger and Exhaust Manifold
  • Replaceable Wet-type Cylinder Liners
  • Corrosion Resistant Components
  • Either-side Service
  • Heat Exchanger or Keel Cooled
  • High Torque and Low Rated RPM
  • Fuel System


John Deere 6068TFM50 (Inboard) Specifications
Horsepower 400-hp
Displacement (cu/cc) 415.00 cu / 6,800.63 cc
Number of Cylinders 6 Cylinders
Fuel Delivery Fuel Injected
Cooling System Raw Water
Weight (lbs/kg) 730.00 lbs / 331.12 kg
Length/width/height 51.2 in / 34.7 in / 27.7 in
Full Throttle RPM 1800

John Deere 6068TFM50 Captain's Report

John Deere 6068

Kadey-Krogen's 58 can be powered with a single John Deere 6090SFM75, 325-hp, but many skippers like the security of twin 158-hp 6068TFM75s for long voyages.

A Diesel for All Reasons

They say "nothing runs like a Deere"; maybe nothing swims like one, either. John Deere engines, including the PowerTech 6068 Series, have been proven in commercial and fishing vessels in the most arduous service, running day-in, day-out, sometimes for weeks at a time, shut down only to change the oil. Many serious cruisers make similar demands on their engines, undertaking long voyages to faraway destinations.

John Deere 6068

The 6068TFM75 comes in three hp ratings; other versions of the 6068 produce up to 400-hp.

If a yacht breaks down, chances are there's no skilled engineer on board to make repairs, so reliability is even more critical in pleasureboat applications. The fact that more and more builders of expedition trawlers and long-range cruisers are delivering their boats with John Deere engines, in both single and twin configurations, tells us all we need to know about the industry's opinion of Deere.

John Deere 6068

A pair of John Deere 6068TFM75s fit nicely in the Krogen 58's engine room.

Our Test Results

A couple of years ago we tested a Kadey-Krogen 58 powered with twin John Deere 6068TFM75 M1 diesels, 158-hp each. The M1 is the lowest-horsepower version of the 6068, an engine intended for continuous-duty in a fishing boat, tug or long-range motoryacht like the Krogen – any vessel that keeps the engine cranking 24/7 for days at a time. (John Deere specs say more than 3000 hrs./year at more than 65% load, 24-hr. uninterrupted operation at full power.) Our test results are below:

John Deere 6068

The Kadey-Krogen 58 we tested had twin 6068TFM75 M1 diesels, so divide the fuel burn figures by two.

Note that our measured figures correlate nicely with John Deere's power curves, below. Knowing you can count on the manufacturer's published data is helpful for picking an engine when you don't have real-world results. We can't vouch for every engine builder, but our tests show that, at least in this case, the Deere curves are very close to what our captain measured.

John Deere 6068

Compare our test results above to John Deere's performance curve for the M1. Deere publishes curves for all its engines; find them on the John Deere website.

Reading a Performance Curve

When reading a performance curve, the "Propeller Absorption" and "Propeller Fuel Consumption" are the relevant curves; the "Crankshaft" curves reflect maximum possible power output and fuel burn at different rpms, but a correctly spec'ed prop pulls 100% from an engine only at max rpm.

The difference between the "Propeller" curves and the "Crankshaft" curves illustrates the diesel's reserve power at each rpm; some of that power is used to drive pumps, alternators and so forth. In head seas, or when heavily laden (say, at the start of a long voyage) or if a prop is damaged, power demand can increase, and the engine produces more power to meet that demand, up to its maximum.

John Deere 6068

Will it fit? Repowering isn’t a do-it-yourself job, so rely on your mechanic or boatyard engineer to determine if the Deere 6068 is the right match for your engine room. Use these dimensions for a preliminary measurement.

PowerTech 6068TFM 75's High Points

For complete specs on the PowerTech 6068 series, surf to the John Deere website and find the section on Marine Diesel Engines; it takes a bit of clicking, since Deere builds engines for almost every conceivable application.

Here are the high points of the PowerTech 6068TFM75 engine we tested; most are shared by other members of the 6068 family. (The more powerful versions have common-rail fuel systems.) --

-- Watercooled turbocharger and exhaust manifold; reduced external connections eliminates hoses and fittings that can leak or break.

-- Either-side service for oil fill and dipstick combinations, with a remote oil filter.

-- High-capacity heat exchanger is designed for reliable operation in adverse conditions; an integrated expansion tank, heat exchanger and exhaust manifold reduce chances of leaks.

-- Keel cooler option provides application flexibility.

-- High torque and low rated rpm let the engine turn larger propellers at lower speed for best efficiency, improve vessel control and maneuvering.

-- Replaceable wet-type cylinder liners are hardened and precision machined for long life.

-- Corrosion-resistant components provides engine protection from the effects of seawater

-- Electronically controlled rotary fuel injection pump with variable timing results in excellent fuel economy and performance; the fuel system features self diagnostics and protection.

-- Emissions Certifications: EPA Marine Tier 2 compliant; IMO MARPOL Annex VI; ABS; Lloyd's; Det Norske Veritas; and others.

Photo Gallery

Engine Image

John Deere's PowerTech 6.8-liter 6068 marine diesel.


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Boats Tested with this John Deere 6068TFM50
Kadey-Krogen 58 Kadey-Krogen 58