Boat Engine Review: MAN V12 2000

The MAN V12 2000 delivers 2000hp (1471kW) from its 24-litre displacement.

Big Torque For Big Boats

MAN's V12 2000 develops massive torque over an incredibly wide rpm range, making it ideal for hefty planing hulls such as Riviera's 22.1 metre (hull length) 78 motoryacht.

Driving 66 tonnes (not including crew and passengers) is another matter and not only does the MAN V12 2000 develop 55 per cent more torque but the torque curve is completely flat from 1200 to 2100rpm.

The peak power output is just as amazing, 74 per cent more for just 48 per cent greater displacement. However the MAN has an “extended” pleasure duty rating (really verging on light duty) of 500 running hours per year compared to the 1000-hour “patrol duty” of the Scania, but this still fits in with Riviera's 2800 hours or seven year warranty protection for selected cruisers. 

<Subhead> In the details

There are no overhead camshafts in this 90-degree V12 engine, just a single gear-driven camshaft and pushrods operating four valves per cylinder. Individual cylinder heads and rocker covers make for easier servicing, just like on a big-ship diesel, and wet cylinder liners transfer heat better. 

Like the Scania, the MAN has high-pressure electronically managed common-rail fuel injection. Not as precise as unit injectors but lighter and simpler. The twin-turbo system with raw seawater-cooled intercoolers helps provide the massive torque from such low rpm and the exhaust gas temperature is a relatively low 533 degrees.

A 24 volt 7.0kW starter motor is standard as is a 28 volt 110amp voltage regulated alternator.

MAN suggests servicing is required every 400 running hours, though changing the oil and filters every 200 running hours or six months will extend engine life. MAN also states the overhaul period is 5000 running hours, very impressive for an engine having these torque and power outputs relative to displacement. No mention is made in MAN's technical specifications of the required fuel density but I presume it's 840 grams per litre in line with other European engine manufacturers and the same as in Australia.

MAN doesn't supply overall length dimensions including gearbox, but the engine is approximately 2200mm long, 1153mm wide and 1272 mm high. Obviously with six cylinders per bank compared to four with the Scania, the MAN is longer, but only 29 per cent (500mm) while it's actually nine per cent narrower (117mm) but five per cent taller (58mm), making it very compact for its outputs.

With a suitable ZF hydraulic gearbox, the Scania weighs 2000kg, whereas the bobtail weight of the MAN is 2380kg. Add the 510kg of the Twin Disc MGX 6620V v-drive gearbox, the largest available in Twin Disc's pleasure boat range, and the total is 2890kg, 45 per cent heavier for 55 per cent more torque and 74 per cent more power.   

On The Water

In Kevin's article, the Riviera 78 displaced around 65 tonnes which gave a better indication of real use performance than had the hull been running minimal tankage. Full fuel tanks alone add 8.6 tonnes to the hull's dry weight.

Sensibly Riviera mounted the engines aft, which although concentrating 5.8 tonnes near the transom allows for midships tankage so the fore and aft hull trim won't be affected as fuel is used. There's nothing new about this, with Sea Ray having done it for years in its inboard sports cruiser range and even Aussie boats such as the Cresta 32 in the early eighties. It's in line with Riviera designing engines in aft hulls across the range, with smaller hulls using Volvo Penta IPS drives.

The engine weight is relatively insignificant in a boat weighing over 65 tonnes; having engines mounted here allows for much more usable accommodation space, such as a dedicated crew cabin ahead of the engine compartment and a full width owner's cabin and bow VIP cabin with two passenger cabins in between. The only drawback is a small tender garage due to the engines being mounted aft, but the foredeck can always be used for larger tenders. 

According to Kevin's figures, at 900rpm and 9.7 knots the total fuel usage was a miserly 26 Lt/h, while at 1400rpm and 11.7kts in semi-planing mode, the fuel flowed at 124 Lt/h.

Cruising at 1850rpm and 22kts the flow was 472 Lt/h, while at the very impressive (especially considering the drag of stabilisers) top end of 2350rpm, the average was 34.1kts using 777.5 Lt/h. All of these figures are well below MAN's factory figures listed in this review, most likely due to slightly under-propping the engines; this allows for much lower fuel-flow than if the engines been propped to reach only 2300rpm with Wide Open Throttle. Being able to cruise fully planing at 22kts shows the efficiency of Riviera's tank-tested 78 MY “warped bottom” hull. 

The Wrap

MAN has a long history of building recreational and commercial marine engines and the V12 2000 shows what years of innovation can produce. It has all the features needed in an engine for planing hulls such as rapid torque rise, is light and compact for its outputs and is fuel efficient. Yet it has big-ship features such as individual cylinder heads and rocker covers made possible only by its conventional valve operation.

For your nearest dealer, Google MAN Diesel/MAN Marine/Seapower and go to Dealer Locator. Seapower is the MAN marine diesel importer for Australia and NZ.

MAN V12 2000 Sea Trial

Note the massive torque rise between 800 and 1000rpm and that 94 percent of peak torque is available at 2300rpm.

MAN V12 2000 Specs

*Brake horsepower/metric horsepower or PS

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