Caterpillar Marine 3000 Family

Built by UK powerboat diesel specialist Sabre Engines Ltd, Cat Marine's 3000 Family diesels were released on the worldwide market last December. All models in the range were designed specifically for motorsailers and semi-planing and displacement-hulled cruisers, and the range comprises two turbocharged and aftercooled models and one naturally-aspirated model.

Unusually in this era of electronically-managed diesels, Cat Marine has opted for fixed-timing mechanical fuel-injection and engine speed governing. But by utilising a rotary fuel-injection pump with an integral electric-stop solenoid and a low-inertia injection system, less engine power is needed to operate the injectors. An air-inlet heater improves starting in low ambient temperatures and the fuel-injection system automatically advances the timing on cold start-up to reduce white smoke.

A custom-designed combustion chamber ensures the right air/fuel mix for optimum combustion efficiency and low fuel consumption and exhaust emissions. This enables the turbo-aftercooled models to comply with current IMO diesel N0x (oxides of nitrogen) emission regulations without resorting to high compression ratios which could reduce engine lifespan. The naturally-aspirated model is not subject to IMO emission regulations.

The turbo-aftercooled models have waste-gated turbos closely matched to the engine's performance characteristics, such as plenty of torque at low revs (though no torque figures were supplied by Cat Marine) to handle the loads for which these models are rated. And cleverly, in view of how these motors will be used, Cat Marine has rated all three models under its 'C' classification, which covers ferries, tugs, tuna and lobster (crayfish) LFBs, short-passage coastal freighters and displacement-hulled motoryachts.

This classification compares directly with Volvo Penta's Marine Commercial Rating 2, just one down from continuous and allowing Wide Open Throttle (WOT) for four hours in every 12 or 24-7 operation at 10% less load than maximum.

Three ratings are available for the models, each known as a Cat 3056. The two turbo-aftercooled models develop 153kW (205hp) at 2500 revs and 138kW (185hp) at 2100 revs, while the naturally-aspirated model develops 93kW (125hp) at 2600 revs.

All models are based on a direct-injection straight six design that has a piston displacement of six litres with a bore of 100mm and stroke of 127mm. In view of the wide variety of applications these motors will be used in, the maximum installation down angle is 17? and up angle (front down) is five degrees. Up to 30? of heel is allowed for motorsailers.

The 'blown' models weigh 609kg in bobtail form (minus gearbox). This is light compared to the nearest European engine, Volvo Penta's 5.5lt TAMD63L which in bobtail form weighs 742kg and develops 173kW (232hp) at 2500 revs under the Marine Commercial Rating 2.

The 'blown' 3056 models have a compression ratio of 16.0:1 and including a ZF Hurth HSW 630 A single-speed gearbox, both motors measure 1401mm x 779mm x 801mm.

According to Cat Marine, the up-rated version uses 42.5lt/hr at WOT but based on a standard propeller power curve at 2000 revs this drops to only 20.4lt/hr with the prop consuming 78.3kW (105hp). At what I presume would be maximum torque and 1600 revs the fuel usage is 10.9lt/hr with 40.1kW (54hp) being consumed, and at 800 revs the usage is a mere 4.5lt/hr.

The de-rated model uses 36.6lt/hr at WOT, 30.8lt/hr at 2000 revs with the prop consuming 119.2kW (160hp) and 15.4lt/hr at 1600 revs and 61.0kW (82hp). At 800 revs this motor uses only 2.9lt/hr, and it would be my choice for passagemaking trawler yachts.

The naturally-aspirated model weighs 595kg bobtail and has a 16.5:1 compression ratio. Complete with a ZF Hurth HSW 450 A single-speed gearbox, it measures 1384mm x 645mm x 801mm.

Cat Marine claims that at WOT this model uses 31.2lt/hr and at 2000 revs 12.5lt/hr where the prop consumes 42.4kW (57hp). At 1600 revs this model uses 7.2lt/hr where 21.0kW (28hp) are consumed, and at 1000 revs and lowest speed quoted by Cat, the fuel usage is 3.0lt/hr. The naturally-aspirated 3056 would be my choice for motorsailers because it can be operated continuously at lower revs without fear of glazing the cylinder bores.

Though small by Cat Marine standards, the 3000 Family of diesels have the same constructional features as their larger counterparts (ie. deep-skirted cast iron block with integral crankcase, which provides rigid support for the forged steel-alloy hardened crankshaft; aluminium-alloy pistons cooled by oil spray and replaceable cylinder liners; valve seat inserts and valve guides; gear-driven fresh and raw-water cooling pumps; and a lubricating oil cooler).

Other examples of Cat's forethought are the Viton crankshaft seals and precision-machined fuel line ends, which provide permanent joint sealing to, says Cat, eliminate oil and fuel leaks. The plate-type oil cooler is built into the crankcase and cooled by engine coolant within the block, eliminating potential oil and coolant leaks from pipe connections common to bolt-on coolers.

Due to the 15lt sump capacity, oil cooler and dual oil filters, Cat Marine recommends an oil and filter change interval of 400 hours. This translates to more than two weeks of continuous 24-7 operation, very useful for trawler yachts which may spend periods this long at sea between ports.

As standard, all models are equipped with a 70 amp hour (A.h) 12V alternator, but a 70 A.h 24V unit is available and a 6kW (8hp) forward power take-off is optional for sail winches, other electrical needs or to drive hydraulics.

Cat Marine's 3000 Family is a welcome addition to the smaller end of the marine-diesel market. Sure, the range is aimed more at heavy-duty operation than light-load recreational applications, but for boaters needing reliable, fuel-efficient and low-emission power for trawler yachts and motorsailers these motors are worth a very close look!

For more information, contact David Moore at Energy Power Systems, tel (03) 9703 4040, fax (03) 9703 4004; or email: david.moore@energypower.com.au.