Cat among the pigeons

Competition in the 700hp category is very stiff, with the Australian distributors of diesel engines vying to provide OEM power for popular cruisers such as the Riviera 47.

Renamed from its 3196 counterpart, the 522kW (700hp) straight-six Cat C12 is yet another engine that provides boat-owners with an alternative to Volvo Penta's 526kW (705hp) D12. And as I mentioned in the recent Cat C30 review, Caterpillar (and MTU/Detroit Diesel) rates its diesels on the traditional horsepower to kilowatt ratio of 1.0hp = 746W, unlike the European and Japanese manufacturers, who favour the Japanese PS measuring system where 1.0hp = 735.5W. Caterpillar says it maintains ISO9000-approved engine test facilities to assure accurate calibration of test equipment.

But unlike the C30, Cat Marine rates the C12 at 25°C of ambient temperature, similar to MTU/Detroit Detroit's rating system - although Cat Marine guarantees maximum power output up to 50°C of ambient temperature. The C12's pleasureboat output is rated at one hour of Wide Open Throttle operation in every 12.5 hours, and up to 1000 hours of operation per year - whereas the 522kW 12.7lt MTU/Detroit Diesel Series 60 has a rating of one hour of WOT in every ten, but to a maximum of only 500 hours per year. Volvo Penta's 12.1lt D12 is rated at one hour at WOT in every ten for pleasureboat usage and up to 800 hours of running per year.

All three engines develop maximum output at 2300 revs and the C12 and Series 60 have maximum cruise revs of 2100 and maximum continuous cruise revs of 1900.

THIRST FOR POWER
The additional torque produced by the C12 over its D12 competition is a real advantage. Admittedly it's produced at 1600 revs and 100 revs higher than the D12, but at 2942Nm compared to 2800, it's a significant increase.

Surprisingly, Cat Marine does not provide torque outputs for the C12 below 1600 revs, and despite numerous requests to MTU-Detroit Diesel Australia I have been unable to obtain torque figures for the Series 60.

According to Cat Marine, the C12 has a WOT fuel consumption of 136.6lt/h, compared to 132.5lt/h for the Series 60 and 136lt/h for the D12. In the maximum torque range of 1400 to 1800 revs, the D12 consumes 39-68lt/h, based on a standard propeller power curve, whereas at 1600 revs the C12 uses 43.6lt/h. At 1600 revs the Series 60 consumes 41.6lt/h.

The maximum continuous cruising revs fuel consumption is 70.2lt/h for the C12 and 68.1lt/h for the Series 60, while at 2100 revs the usage is 96.5 and 94.6lt/h respectively.

TALE OF THE TAPE
Where the C12 really scores over its direct MTU/Detroit Diesel and Volvo Penta competition is with its relatively light weight. The Series 60 has a bobtail (minus gearbox) weight of 1589kg and the D12 1400kg, but the Cat C12 weighs only 1177kg - an enormous difference in a boat such as the Riv 47.

The C12 has an overall length of 1875mm, width of 969mm and height of 1005mm, compared to 1719 x 995 x 1154mm for the Series 60 and 1790 x 1027 x 1177mm for the D12. So although the C12 is slightly longer, it's significantly lower - most likely a result of staying with pushrods instead of opting for OHC layouts.

Standard C12 equipment includes a corrosion-resistant seawater aftercooler, similar to the Series 60 - whereas the D12 has a freshwater-cooled system. Both the raw (sea) and heat exchanger waterpumps are gear driven, and the expansion tank is integral with the heat exchanger, which has a removable tube bundle and replaceable copper-nickel tubes. The thermostat is designed to be fully open at an efficient 92°C.

The fuel priming and fuel transfer pumps and fuel filter is handed for twin-motor installations, to starboard on the port motor and port on the starboard unit, as are the crankcase breather (closed circuit), engine oil cooler, canister-type oil filter and dipstick. A PTO is also standard for powering hydraulic pumps and can handle up to 77Nm of torque.

Accessory equipment includes air starting, 12 or 24V alternators up to 60amp, a cooling water jacket heater for very cold climates, an OEM wiring harness and a spare parts kit.

SENSIBLE MANAGEMENT
As regular readers of Trade-A-Boat know, I'm a keen advocate of electronic management systems in marine engines. Provided they're fully waterproofed, cooled effectively and isolated from engine vibration, there is no logical reason why a system should ever fail. For example, Cat Marine's Electronic Control Modules are sealed to operate at a depth of 21m!

Random factory testing also subjects ECM diesels to extreme heat, cold, vibration, dust and electromagnetic interference under controlled conditions to simulate real life situations.

And this reliability is what Cat Marine emphasises to potential buyers of its electronically-controlled models, because ECMs also have a memory function that records problems such as faulty fuel injectors and the resulting incomplete combustion in one of the cylinders. The ECM records engine hours, fuel consumption and load factor, such as hours spent idling in a specific period of time.

The ECM sensors measure inlet air and fuel supply restriction, low oil pressure, abnormal crankcase pressure and exhaust temperature, and overheating of the engine coolant and transmission oil. Sensors placed at strategic points around the motor update information 20 times per second, and this information can be relayed to a shore station via Satcom. So should a problem arise at sea, service personnel can meet the boat when it docks - saving a lot of downtime when the big fish are running!

The C12's ECM enables multi-engine installations to be easily synchronised - and even a single throttle used if required - while ensuring that each engine maintains steady revs according to the throttle setting.

A suitable single-speed gearbox for the C12 is the Twin Disc MGX-5114A with the clever 'Quick Shift' facility and seven-degree down angle at the output flange. This box adds 206kg (dry) to the bobtail engine weight.

For more information on the C12, contact Garry Dann at Energy Power Systems, tel (07) 3272 1677 or email garry.dann@energypower.com.au.