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Big Dog

Caterpillar announces its new C32B Triple Turbo, the most power available in a 12-cylinder package on the water today.

Caterpillar C32B Triple Turbo Marine Engine

Caterpillar C32B Triple Turbo Marine Engine

Last year, Caterpillar put a new version of its time-honored C32 diesel platform on the market—the C32B Tier 3 Recreational Diesel. That particular engine, rated at 2,000 bhp or 2,025 mhp (the latter being a European measurement which, for various reasons, is 1.0139 times the American standard set by the Society of Automotive Engineers), was more powerful, capable of generating more boat speed and, according to CAT, quieter than the company’s long-standing flagship product, the 1,925-mhp C32 ACERT that’s been serving battlewagons and big motoryachts for well over a decade. The C32B Tier 3 also met EPA Marine Tier 3 and International Maritime Organization (IMO) emissions standards, according to Caterpillar.

Now, the company’s Houston-based marine division has come up with yet another, more power-dense version of the C32—the 2,400-bhp or 2,433 mhp C32B Triple Turbo. And while certain aspects of this new beast replicate the basics of its progenitors—the displacement and core architecture of the older C32 models are generally maintained—there are some significant modifications that seriously facilitate what we expect will be a serious boost in on-the-water performance.

Most noteworthy, perhaps, is the triple-turbocharging feature. Instead of two parallel turbochargers, the new engine has three sequential units (a central turbo that operates at slower speeds and two outboard turbos that join the parade as speeds increase) that, according to CAT, seamlessly climb the torque curve without noticeable lag.

Increased turbocharging, of course, means that increased heat is generated throughout the engine and to deal with this issue, Caterpillar has not only plumbed a substantial seawater pump into the raw-water cooling system in the conventional manner, but has also plumbed an additional seawater pump into the engine’s aftercooler, thereby helping to remove extra heat from the highly compressed discharge air emanating from the compressor sides of each of the three turbos.

CAT says the new engine is going to be approximately 25 percent quieter than older C32s at idle or trolling speeds, although the company did not have exact dB(A) comparisons available during a recent press event. “We use what we call a ‘split shot’ injection technique,” said Caterpillar product strategy engineer Allen Boman, “and this helps reduce the noise. We’ll have further information on sound in the near future.”

Split shot?

For starters, the new C32B is not a common rail engine. Instead, it uses individual, electronically controlled, cam-energized unit injectors to deliver fuel to each of its 12 cylinders in two separate or split shots, the first a relatively small “pilot” burst, followed by a second, “main” or larger burst. Although Bowman said that breaking up the injection process in this way “dampens combustion noise,” he was reticent about discussing the process in further detail. “This aspect of our technology,” he said, “is something I’d rather not share at the present time.”

While, as noted earlier, core aspects of the new C32B Triple Turbo replicate those of earlier models, the crankshaft, connecting rods, pistons, cylinder head, certain aspects of the block and other basic components have been strengthened to accommodate a 20 percent increase in power output. Moreover, software adjustments have been made. And, according to CAT, the new engine also meets EPA Tier 3 Recreational and IMO II emissions regulations, and if an owner or builder opts for it, there’s a Selective Catalytic Reduction (SCR) system that makes the engine compliant with IMO III regs.

Footprint dimensions remain substantially the same as previous models, and duplex fuel and lube filters are available, along with left- and right-handed service point configurations. There are no zinc anodes—Caterpillar maintains that as long as the engine is robustly connected to a given boat’s bonding system, zincs are unnecessary.

The Caterpillar C32B Triple Turbo is expected to show up out on the water this summer on several try-out boats from a variety of manufacturers. Orders for the new engine will be officially taken later this year, and actual deliveries are expected to occur in 2022.

“We’re very excited to build on the recent introduction of the 2,025-hp C32B by bringing even more power density to market,” product strategy engineer Bowman concluded in a press release. “This new engine will be a real difference-maker for the high-performance marine segment, both in power and performance. We think it’s an outstanding product.”