IN THE WORLD of large, high-speed diesels, MTU is a reigning monarch. Aside from the sheer muscle in its engines — which ranges up to 10.000 hp — this German enginebuilder’s claims to fame are an impressive power-to-weight ratio and slick engineering.
At 1,873 shaft horsepower each, the 12V396-TB93s in the Bertram 72 develop an extremely favorable ratio of 6.0 pounds per horsepower. This is achieved by combining German engineering elegance with real-world practicality in powerplants that are designed from the ground up to be marine diesels.
For instance, our Bertram's MTUs feature a one-piece forged crankshaft (DDC’s larger packages use bolted-together assemblies) supported in sleeve bearings. The powerplants also have forged connecting rods, cast-iron cylinder heads with replaceable valve seat inserts, centrally located fuel injectors with an oil-tight separation between the lube oil and injector chambers, composite pistons, and two turbochargers, one for each cylinder bank.
This four-cycle design also has a cylinder cutout system which helps eliminate smoking at low speeds by cutting off the fuel to one bank in the 90-degree V-arrangement. This also makes MTUs very quiet when maneuvering around docks and marinas.
Another feature is Monitoring One. a microprocessor-controlled system which activates the cylinder-cutout mechanism and has an alarm system and gauges to monitor engine temperatures and pressures. lf a problem develops in the fuel system, for example, the engine will automatically cut back to a safe operating range until the malfunction is corrected, at the same time pinpointing the source of trouble.
Because of the engine's sophistication and complex systems, MTU expects the owner or captain to maintain the machinery religiously. That's pretty painless though, when you consider the payoff in speed, efficiency, and longevity. In typical yacht application, MTU figures you'll get at least 6,000 hours (10 years) out of one of these 12s before it needs a complete overhaul; and throughout this period, the power to the propshaft should remain constant. This means your boat probably will run as fast after several seasons as it did when brand-new. And that's power hard to beat at any price.
This review/article originally appeared in Boating Magazine, May 1990 and is written by Peter Frederiksen. For more great powerboat reviews, visit their website and subscribe at: http://subscriptions.boatingmag.com/