John Deere Power Tech 4024T marine engine review

When my mate Ken was shopping around for an auxiliary engine for his 44-foot (13.4m) steel trawler yacht Noble Tasman, he logically decided John Deere was the route to go. After all the main engine was a John Deere so why not the auxiliary?

Checking out what John Deere had to offer he settled on a Power Tech 4024T industrial diesel which had the power and torque to get him home should the main engine fail. Ken had closely studied other production yachts with auxiliary wing engines, some of which could provide no more than 3kts. That was plain inadequate and 5kts would be a better cruise, so the auxiliary was way more than just a toy for slipping up rivers.

Sure his main 6068 diesel could idle along at 5kts using a mere 4lt/h, but at 1100rpm it is way too low for continuous running as the cylinder bores could glaze due to the fuel being injected too early. All mechanically managed diesels have their injection timing set for maximum torque, so running well below this is really detrimental for engine longevity.

The 4024T was not set-up for heat exchanger freshwater cooling but this wasn’t a problem as the 6068 already had keel cooling with a dry exhaust and the 4024T could tap into this system, keeping saltwater well away from the engine.

TURBOCHARGED DIESEL

The John Deere Power Tech 4024T is a straight turbocharged indirect injection engine displacing 2440cc and developing 66 brake horsepower at 2800rpm. Unusually the four-cylinder engine has hydraulic valve lifters eliminating the need for regular valve clearance adjustments.

The usual indirect injection engine glow plugs are fitted for cold starting and like the 6068 the 4024T has mechanical fuel injection, so the engine lasts longer when run continuously above its maximum torque band which peaks at a low 1600rpm. Maximum torque is 221Nm, so like the 6068 the powerhead isn’t stressed.

A naturally aspirated engine of this displacement would produce around 170Nm at similar rpm and a turbo-intercooled engine about 350Nm, so the 4024T produces useful extra torque without affecting engine lifespan. Being turbocharged the compression ratio is a relatively low 19.1:1 compared to around 23:1 for a naturally aspirated engine. But still there’s no provision for hand starting (phew!)

Without a gearbox the John Deere Power Tech 4024T is 662mm long, 566mm wide and 772mm high. Part of this height is due to the long piston stroke and the alternator being mounted next to the rocker cover. At 251kg bobtail weight (minus gearbox), the 4024T is not exactly light and a suitable box adds around 30kg to the dry weight.

To reduce hull drag when the main engine was being used Ken chose a 1.9:1 gear reduction ratio Borg Warner box driving an 18 x 13in two-bladed right-hand Gori folding prop. The shaft angle of around eight degrees is steeper than the main engine’s four to five degrees, but this was unavoidable as the shaft exits through the bottom plating and not through an aperture in the keel.

SERVICING

Servicing the John Deere Power Tech 4024T is straightforward with the canister oil filter easily reached. Like the 6068 the John Deere 4024T has an expansion or overflow tank for the cooling system to eliminate the need for frequent coolant top-ups when the engine is stopped after a long run. For longevity the cooling water pump impeller is in a cast iron housing.

Oil and filter changes should be every 200 hours or annually and I recommend using a good quality diesel SAE15W40 oil. Higher viscosity oils such as monograde 30-weights should not be used as the oil has to quickly fill the hydraulic lifters from cold when turning over the engine.

PERFORMANCE

Like its way more powerful engineroom mate the 4024T started instantly cold with no grey smoke appearing or black smoke when it was run out to Wide Open Throttle. As expected of a four-cylinder engine versus a straight six vibration levels were much higher, but part of this came from the thump of the prop blade tips when they passed close to the relatively flat bottom plating.

Noise levels at cruising rpm were also higher, understandable as the engine was revving twice as fast as the 6068 at 5kts. All the same, performance was pretty damned good considering the John Deere Power Tech 4024T was pushing 26 tonnes!

Up to 2200rpm the prop bit well into clear water ahead of it but above this rpm suffered from cavitation which actually reduced hull speed. I think a three-bladed Gori prop of slightly smaller diameter would have worked better and preferably one with the incredible “overdrive” feature so the engine could be loaded up more at low rpm. But only in calm water as turbocharged engines have to be able to reach their designed rpm at WOT.

THE VERDICT

As I have stated countless times before, opting for industrial diesels in displacement hulls makes good sense. Their maximum torque outputs at relatively low rpm make low-speed handling a pleasure and they are designed for a hard life in tough conditions. And few conditions are tougher for engines than the marine environment!

In my opinion the 4024T could also handle the way easier life of pushing displacement cruisers from 8 to 8.5m, providing they were designed for keel cooling and a dry exhaust.

For more on this engine, contact Steve Shale at Marine Diesel, phone (07) 3390 3633 or email: admin@marinediesel.net.au

POWER TECH 4024T PERFORMANCE

Single 66hp John Deere Power Tech 4024T wing engine with two-way runs on Lake Macquarie, NSW, using onboard GPS and John Deere fuel flow figures, calm water

* Severe prop cavitation above 2200rpm.

JOHN DEERE POWER TECH 4024T SPECIFICATIONS

TYPE Four-cylinder turbocharged diesel engine

RATED HP 66 at 2800rpm

TORQUE 221Nm at 1600rpm

DISPLACEMENT 2440cc

BORE X STROKE 86 x 105mm

WEIGHT 281kg (dry w/ gearbox)

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Originally published in Trade-A-Boat #460, December 2014 / January 2015. Why not subscribe today?