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New Marine Engines

A Powerful Year Ahead

Engine manufacturers created a lot of exciting buzz
at the Ft. Lauderdale and Miami shows.

CAT’s new C7.1


On the heels of the C8.7 and C12.3 it introduced last year, Caterpillar unveiled yet another new propulsion engine for recreational boats, the C7.1. This in-line six-cylinder engine, based on a model used in CAT gensets, is available in three ratings: 507, 456, and 406 horsepower, all at 2900 rpm. All versions of the C7.1 meet EPA Tier 3, IMO II, EU Recreational Craft Directive and EU Stage IIIA regulations. 

The Cummins Onan division announced  a new Tier 3-compliant genset for 2016, the MDDCM that features an advanced sound shield for lower noise levels and a new mounting system that reduces vibration. It joins the company’s extensive Tier 3-certified marine line, which includes engines from 6.7 to 50 liters and generators from 17 to 55 kilowatts. 

A lot happened at the MAN booth at the Ft. Lauderdale International Boat Show last November, namely the introduction of a couple new 12.4-liter, in-line six-cylinder diesels—the i6-730 and i6-800. They’re based on MAN’s D2676 engine and feature the latest iteration of the company’s common-rail fuel injection, which generates an impressive 26,100 psi of fuel-delivery pressure. The 800-horsepower i6-800 cranks out 1,991 pound-feet of torque between 1200 and 1900 rpm, which should ensure quick planing. Equally impressive, both it and the 730-horsepower i6-730 weigh just 2,645 pounds. MAN also unveiled a new version of its 24-liter V-12 rated at 1,900 horsepower, a jump of 100 horsepower over the previous rating, which will continue to be offered. The V12-1900 is rated at 2300 rpm and weighs just 5,213 pounds dry.

Most of the attention at the MTU booth focused on ratings for the 12- and 16-cylinder 2000 Series engines that were introduced last year. Designated M86, they are 1,700 and 2,186 horsepower at 2450 rpm respectively. Both engines feature common-rail fuel systems and triple turbochargers that engage sequentially.

The Yanmar 6LY2A in-line six has been a favorite for decades for reliability and horsepower-to-weight ratio. Now Yanmar has added common-rail fuel injection to it, resulting in the 6LY400 and 6LY440. (The last three numbers indicate horsepower.) The 5.8-liter block is essentially unchanged, as is the dry weight of 1,230 pounds, meaning the horsepower-to-weight ratio is better. Both engines comply with U.S. Tier 3 and EU RCD 2016 emissions standards.

Gas Inboards

The news in gasoline inboards is not so much new engines as where the engines are coming from. As we discussed here last month, Volvo Penta introduced a pair of state-of-the-art V-8s featuring direct injection and variable valve timing. Volvo sources this duo, like the rest of its gasoline engines, from General Motors, with which it has had a long relationship.

Mercury has enjoyed a long relationship with GM—until recently. In fact it was GM’s biggest marine customer. But Mercury severed that relationship and now manufactures all of its own gasoline engines. They include 375- and 425-horsepower versions of an 8.2-liter V-8 and 300- and 350-horsepower versions of a 6.2-liter V-8, both designed for inboard applications. On the stern drive side the lineup includes the same 6.2-liter V-8s plus a 4.5-liter V-6 rated at 200 or 250 horsepower, a 4.3-liter V-6 rated at 180 or 220 horsepower and the venerable 135-horsepower 3-liter in-line four that Mercury has been building for years.

What’s particularly interesting about all this is that compared to the Volvo-GM engines, the MerCruiser models are low-tech; that is their engine blocks are cast iron instead of aluminum and they lack direct injection and variable valve timing. The MerCruiser engineer I spoke to argued that these technologies are “inappropriate for the marine duty cycle,” but surely cost is also a factor. I have to believe MerCruiser’s engines will cost boatbuilders a lot less. It’ll be interesting to see how much of that savings gets passed on to consumers.

MerCruiser is also offering an array of direct-injected Tier 3-compliant diesels in 2-liter four, 3-liter six and 4.2-liter V-8 configurations ranging from 115 to 370 horsepower based on engines from Volkswagen and the Italian manufacturer VM Motori. 

And finally, Ford is back in the gasoline marine engine business. Indmar, which produces engines primarily for the waterski towboat market, is offering three versions of the Raptor, based on the 6.2-liter single-overhead-cam V-8 that Ford installs in F Series pickups. Two of them, rated at 400 and 440 horsepower, are marinizations of that engine (which Ford introduced in 2011), and feature a cast-iron block and aluminum heads, two sparkplugs per cylinder and variable valve timing; the third version, developed by Roush Motorsports, adds a supercharger to increase the output to 575 horsepower.

This article originally appeared in the May 2016 issue of Power & Motoryacht magazine.