MERCURY

words - Andrew Norton
Cummins MerCruiser Diesel's 2.8 ES 200 can hold its own compared to V8 petrol sterndrives, reports Andrew Norton
Uprated from its predecessor, which developed 163hp at 3700rpm, Cummins Mercruiser Diesel's recently-released 2.8 ES 200 now develops 197hp at the crankshaft or 189hp at the prop, both outputs at 3800rpm.

CMD says the 2.8lt four cylinder engine, which has a 94mm cylinder bore and 100mm piston stroke, has been extensively re-worked by fitting new pistons and rings to handle the increased combustion pressures and temperatures and reduce piston ring oil-blowby, while the piston oil jets have been relocated to improve cooling under load.

The intercooled turbocharger provides more torque at lower engine revs for better planing performance, while exhaust emissions are further reduced by using dual-stage fuel injectors.

But perhaps the biggest change is the addition of twin counter-rotating balance shafts, similar to what Volvo Penta has done with its D4. Four-cylinder engines always provide better fuel efficiency than comparable-displacement straight-six engines but because of the two pistons up and two down configuration of a four-cylinder engine, balance shafts are necessary in any engine over 2.2lt.

Other changes include relocating the heat exchanger, freshwater cooling pump and electrical wiring to the side of the engine to reduce overall length by 101mm from the 2.8 ES 165. But fortunately the low-maintenance hydraulic valve lifters operated by pushrods from a side-mounted camshaft remain and the removable cylinder liners and individual cylinder heads simplify in-boat servicing.

Comparing the 2.8 ES 200 to petrol V8s
Because of the maximum torque being produced at only 2200rpm it's very hard to compare the 2.8 ES 200 with a petrol V8. The relatively flat torque curve of the 2.8 ES 200 enables the engine to produce 380Nm at only 1800rpm, 430Nm at 2200–2600rpm and 370Nm at 3800rpm.

Although Mercury Marine is reluctant to release torque figures for its petrol sterndrives, my automotive contacts said the 5.7lt V8 fitted to the current model Holden Commodore produces 470Nm at a high 4800rpm, so the MerCruiser version should produce somewhere between 400–450Nm in the 3000–4000 rev range.

The 5.7lt 350 MAG MPI Horizon develops 300.3hp at the prop at 4800rpm and based on the 2.8 ES 200's lower Wide Open Throttle rev range this engine should provide similar performance. However the MerCruiser MX 6.2 MPI Horizon develops 320.4 propshaft horsepower at 5000rpm and about 430–480Nm in the 3000–4000 rev range.

The Horizon models were chosen for comparison because like the 2.8 ES 200 they have heat exchanger cooling, which in my opinion is essential for a boat left permanently afloat. And like the V8's the 2.8 ES 200 has full electronic engine management which alters the fuel injection spray timing according to engine load to prevent fuel oversupply when the hull starts to plane.

The 2.8 ES 200's fuel consumption is low for its output and based on a standard prop power curve the flow rate is 21.2lt/h at 1800rpm, 25.7 at 2200rpm, 30.3 at 2600rpm and 45.4lt/h at 3800rpm. Compare these figures to 42.7lt/h at 3000rpm, 65 at 4000 and 92lt/h at 5200rpm for a 350 MAG MPI Horizon and 41.0, 56.0 and 88.0lt/h at 3000, 4000 and 4700rpm for the 6.2lt V8. At 3000rpm the 2.8 ES 200 uses 34.1lt/h but really the output at these revs is approximately equivalent to the MerCruiser's at 4000rpm and frankly a massive fuel efficiency increase.

Comparing dimensions and features
The engine-only dimensions of the 2.8 ES 200 are 944mm long, 767 wide and 790 high, compared to 813mm long for the 5.7 and 814 for the 6.2, while the widths are the same at 740mm. the heights are 559mm but this measurement is taken from the crankshaft centreline and CMD doesn't state if this also applies to the 2.8 ES 200.

Despite the power and torque increases over the 165 the 2.8 ES 200's weight is no greater and with a single-prop Bravo Two X leg the 2.8 ES 200 weighs 493kg, while the twin counter-rotating props Bravo Three X version weighs 497kg. The 350 MAG MPI Horizon and MX 6.2 MPI Horizon both weigh 482kg with the Bravo Two leg and 486 with the Bravo Three leg although these are not the X models. Amongst the petrol MerCruiser sterndrives only the 8.1lt 496 MAG HO, which develops 425hp at 4800rpm and weighs 551 or 556kg, is available with Bravo One, Two or Three X legs.

Like the V8s the 2.8 ES 200 has a serpentine drive belt for the seawater cooling pump, alternator and power steering, not only making replacement easier but also reducing side load on the pulley bearings as occurs when more than one belt drives from a pulley. The alternator is mounted well up the engine block and the exhaust elbow from the turbocharger is almost at the same height as the rocker cover. The alternator and engine management computer are protected from by a plastic shroud from damage and the engine oil filter is easily reached for replacement.

The X legs have cooling water intakes located just above the gearcase torpedo and well forward for optimum pickup in broken water and like their Bravo counterparts cone clutches are used with remote checking of leg oil level. For twin engine installations counter-rotating Bravo Two legs would give better low speed hull control than the Bravo Three leg (unless a bowthruster is fitted) but the latter is my recommendation for single engine installations.

For more details on the Cummins MerCruiser Diesel 2.8 ES 200 email murray.clifford@cummins.com or visit http://www.cmdmarine.com/ for your nearest CMD dealer.



Published : Thursday, 1 September 2005

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