When most people think of diesel engines, a few specific vehicles or applications come to mind. Typically, these would include buses, semi-trucks, heavy equipment, tractors, and other utilitarian applications. While many parts of the world are more accustomed to seeing diesel engines in passenger cars, this is a fairly new concept to the United States.
Previous articles have covered the use of diesel engines in aviation as well as a single fuel concept within the military, regardless of the specific application. Diesel engines pushing watercraft up rivers and across the open seas isn’t exactly a new idea – most are familiar with giant cruise ships, ocean liners, and tugboats. What isn’t so commonplace, is using diesel engines in marine applications that require speed and agility.
Offshore fishing boats and luxury yachts have been utilizing the benefits of diesel engines for many years. Between efficiency, the ability to produce tons of torque, durability, and reliability – the diesel platform is a solid choice for any seaworthy vessel. For this segment, we would like to focus on a few diesel marine applications that are not as common, and take an overall look at these incredible machines.
The World’s Fastest Diesel Boat, The XSR48
This vessel has been referred to as the world’s fastest diesel superboat, a term spun from the word supercar which is used only to describe the fastest, rarest, and most exotic automobiles the world has to offer.
Most boats built for speed typically utilize two or three high-horsepower gasoline engines that can run at consistent high RPM, and produce a lot of horsepower. Some even go to lengths to run turbine engines in their speed boats. However, we are here for a love of the diesel engine, and thats exactly what this boat runs with – two of them to be exact.
This vessel flys across the surface of the water thanks to two 11.3-liter Isotta Fraschini L1306 twin-turbo engines. The L1306 is an in-line six-cylinder with 130 mm bore x 142 mm stroke. While this engine can be ordered in a few different configurations, the XSR48 houses the 2,000 horsepower variety. Other versions offer substantially less horsepower, and operate at lower RPM to conserve fuel, and extend engine life.
As we had mentioned, a lot of high-performance boats use gasoline engines in part for the wide RPM range in which they can operate. Effectively these engine’s RPM range allows the prop(s) to spin at a wide RPM range which to propel the boat from an idle to high speeds. Prop designs can be changed for different effects here as well but for the purposes of this article we are looking solely at engine variations.
LOA (Length Overall) – 47.9 feet
Beam – 8.5 feet
Draft – 2.6 feet
Total Weight – 14,770 pounds
Fuel Consumption – at 70 knots, 58 gallons per hour
Fuel Consumption – at 56 knots, 42 gallons per hour
Fuel Capacity – 290 gallons
Because these diesel engines operate in a much narrower RPM range, the boat designers needed a way to spin a high-speed prop at lower and higher speeds. This was done through the use of a two-speed gearbox, the ZF 312 to be specific.
Bolted to the gear box are a pair ZF 2200 outdrives, which are known in the boating world as surface drives. Quite simply, this means that when the boat is on plane, the tops of the props actually pierce the surface of the water. A pair of Rolla 17/4 pitch stainless steel props push the water, while Trimax composite trim tabs and rudders handle the ride adjustments and steering.
While some of this may sound a bit unfamiliar to those not used to watercraft, the import factor here is that diesel technology has afforded this awesome boat with a cruising speed of 50 knots (or 57.5 mph), a range of 300 nautical miles (345 miles) at cruising speed, and maximum speed of 85 knots or (97.8 mph).
The boat was constructed under the company XSMG which was founded by Ian Sanderson and Peter Dredge, who together have broke more than 10 world records in the boating world. To ensure their success on this project, they enlisted some talented help to say the least. The hull and hydrodynamics were created by legendary speedboat designer Fabio Buzzi, while award-winning super yacht design firm Redman Whiteley Dixon took care of the interior styling and design. The XSR48 was built in Lymington, England and initially launched in December 2006. In addition to touring around the world, the boat was featured on an episode of Top Gear on the BBC.
From its roaring twin-turbo diesel engines, to the exotic looks both inside and out, to the carbon fiber toilet, we just loved every aspect about this vessel. Needless to say it is quite expensive, and reaching past the seven-figure mark we’ll just say it falls into the “If you have to ask, you can’t afford it,” category.
This particular vessel was crafted for a very specific purpose, and being that it was not built to ever be in production, it is the only one like it. As appropriate as it would seem to see James Bond 007, or an evil mastermind behind the wheel, the purpose of this boat is divulged right in its name – to break the world record in a powerboat for circumnavigating the globe.
While the shape of the boat provides quite an interesting aesthetic, it actually serves several different purposes. The long and narrow wedge shape enables it to pierce through waves rather than riding over the top of them like a traditional displacement hull. The bow of the boat rides very low to the surface of the water, and the boat is capable of submarining to a depth of about 23 feet, meaning it can drive straight through a large wave and exit the other side while still underway … quite amazing.
The large horns you see topside are an integral part of the design, as they are air ducts for the engines. The air that heats up around the engines is expelled through these horns, while cool outside air is sucked through the lower ducts and funneled underneath. Miraculously, this process is completely done through convection. When the craft is submerged beneath a wave, all water ingress is automatically ducted out the sides, and because she only stays submerged for seconds at a time, there is enough air inside the engine rooms to keep the diesel engines running underwater.
You may be wondering what it is that powers this futuristic-looking craft with the torque to push through water when fully submerged, yet maintains the economy and reliability needed to travel around the earth. No big surprise here, diesel was selected again. In fact, Cummins Mercruiser Diesel supplied the engines for Earthrace, and produce a combined output of 1,080 horsepower. Both engines utilize common rail technology like all of the modern light-truck engines and turbochargers, which can generate boost up to 45 psi. Instead of a typical air-to-air intercooler like those found in on-road applications, the boat uses water-to-air intercoolers by picking up raw seawater and passing it through the intercoolers.
Seawater is also used to the engines by passing it over a heat exchanger which cools the engine coolant down. Finally, seawater is mixed with the exhaust gases before exiting the hull to help with cooling and muffle the exhaust note. To ensure the Cummins engines are burning the purest diesel possible, all fuel passes through a 10 micron Racor 75/100 max fuel filter, and a secondary 2 micron fuel filter before entering the high-pressure fuel pump.
Hull Design – Wave-piercing Trimaran
Designer – Craig Loomes Design Group
LOA (Length Overall) – 78 feet
Beam – 24 feet
Draft – 4 feet
Range – 6 knots, 13,000 nautical miles
Range – 25 knots, 2,000 nautical miles
Maximum Speed – 40 knots
Fuel Capacity – 3,000 gallons
Dry Weight – 14 tons
Wet Weight – 26 tons
Earth race’s 1,080 horsepower runs through a pair of single-speed ZF-305A gearboxes built by ZF Marine, which provides the vessel with forward, neutral, and reverse. These gearboxes have a drive ratio of 2.423:1 – meaning that for every full turn the propellers make, the engines have turned 2.423 revolutions. ZF also provided the throttle controls, which can be manipulated independently for turning, or linked together to maintain identical power outputs from each mill.
The ocean is the foundation for many hobbies and passions the world over, from scuba diving, to fishing, surfing, and sailing. Because the ocean is a home to so many plants and sea creatures, many of those who take to the oceans for fun are also highly concerned about keeping her clean. Fortunately, this vessel runs solely on biodiesel, and any seawater that is ingested for cooling passes through filters to trap any pollutants before returning to the sea.
In fact, Skipper Pete Bethune mentioned, “Earthrace’s success has proved that any form of transport, including marine, can be non-damaging to the environment while still maintaining high-performance. Although these are early days for alternative fuel and there are issues that need to be addressed by those with the power to make change happen. But, I hope that Earthrace and her adventure highlight to the world the importance of continuing to research alternative fuel sources for global use.”
To this point, the boats we have looked at have been propelled by diesel engines to utilize the power and reliability commonly associated with the diesel platform. While achieving top speeds with luxurious amenities and circumnavigating the globe are important to the owners and helping to push technology, some could argue that the next ship we want to look at has the most important job of all – protecting a country and its people.
The final vessel we’d like to examine was constructed by a Swedish shipbuilder, known as Dockstavaret, and goes by the model name of CB90. While typical operations for the vessel include combat, special operations support, search and rescue, and the like, these awesome boats can also be outfitted to perform as an ambulance or a fire rescue vessel.
Generally speaking, this boat is what is known as a “fast attack boat” which, thanks to its overall design, speed, agility, has the ability to deliver a large group of troops into a combat zone though rough and shallow waters. It also has the capability to be both defensive and offensive while underway if necessary. Constructed from an extremely lightweight aluminum frame, it can carry 21 combat-ready troops, plus gear, a captain and a helmsman, along with all other provisions at a high rate of speed.
The amount of armament outfitted to the CB90 is enough to make even the most brazen of adversaries question their engagement. It typically features two forward-mounted 12.7 mm Browning heavy machine guns, and a third machine gun (or a 40 mm automatic grenade launcher) mounted aft of the wheelhouse. It can also support a Hellfire Surface-to-Surface Missile (SSM) anti-tank system, and four sea mines, or up to six depth charges.
The Amos gyro-stabilized, twin-barrel, 12 cm mortar is also found near the stern and can deliver up to 26 rounds per minute while underway. Weapon choices change depending on the missions at hand but many CB90s have since subbed out the 12.7 mm Brownings for 7.62 mm automatic weapons due to a significantly increased rate of fire.
Operational Range – 240 nautical miles at 20 knots
Crew – 23
As you can imagine, all of this mass must require some serious torque and power to move across the water at such speeds. These boats are powered by a pair of Scania DS114 engines, which is a turbo-diesel V8 engine producing around 1,250 horsepower. The 2,500 horsepower duo generates thousands of pound-feet of torque generating some seriously impressive speeds.
Each powerplant spins a twin-ducted Kameqa FF water jet propulsion system. This type of propulsion system plays a large roll in the shallow water accessibility of these boats, in addition to the ability to make extremely sharp maneuvers at speed.
Boats typically lack the ability to slow down quickly, relying on the massive amount of friction to do the braking, and a little reverse throttle when maneuvering around at idle speeds. The CB90, however, is equipped with a device that allows the boat to decelerate from 40 knots to sitting static in a mere 130 feet, or two and a half boat lengths — now that would be an E-ticket ride!