Volvo Penta’s zeal for designing powerful engines with low emission for planing boats continues in the D6-370. It shares common characteristics with the other diesels engines in the lineup in that she has a common rail fuel injection system, double overhead camshafts, 4 valves per cylinder, turbocharger and aftercooler and is controlled by the company’s proprietary EVC (Electronic Vessel Control). Volvo Penta makes it available in inboard, sterndrive and IPS configurations and it’s purpose built for the marine environment.
Volvo Penta D6-370 Captain's Report
The Volvo Penta D6-370 has a crankshaft output of 370-hp (272 kW), a max torque of 883 Nm (651 lb./ft) at 2000 rpm and weighs 1,698 lbs. (770 kg), including outdrive.
Volvo Penta created the D6-370 to provide a clean burning engine with high torque specifically suited to the marine environment. This is not a tractor or truck engine that got a makeover for the boating application. This engine was purpose built for boating and as such has the appropriate power to weight ratio and torque curved needed to succeed.
Mechanical Compressor. This produces high charge pressure to produce maximum torque directly from low speeds. This is a key feature in producing the powerful acceleration demanded from planing boats.
Attached Filtration. Water, fuel, and oil filters are all attached to the engine and typically are working in conjunction with separate filters for fuel already installed on the boat for primary filtration.
115 Amp Alternator. The engine can also accommodate a second alternator that can be dedicated to the ship's systems.
Low Vibration. In addition to vibration dampening engine mounts, Volvo Penta builds engine strong for minimal vibrations which further reduces vibrations transferred to the hull.
To further strengthen the design of the D6, a ladder frame is bolted to the base of the engine block. The in-line configuration allows room for a well-dimensioned crankshaft with large bearing surfaces.
Aftercooled. A large white rectangular component at the rear of the engine is the aftercooler. Its job is to cool the air from the turbocharger from roughly 300-degrees to a more usable 110 to 120-degrees. And since cool air is more dense than hot air, the engine burns much more efficiently.
The aftercooler turns hot air into cooler air so more air molecules get into the combustion chamber.
Turbo-charged and Supercharged. While the turbo is exhaust driven the supercharger is belt driven with an electromagnetic clutch. This allows the supercharger to be computer controlled and the computer, in turn, decides when to engage and disengage the unit. For example, when the captain firewalls the throttle, the computer senses that more power is needed and engages the supercharger. When the speed settles, the supercharger is disengaged.
Hydraulic Valve Lifters. This is one of the only engines in class that we’re aware of that utilizes hydraulic valve lifters. The long and short of this benefit is that we never have to adjust the valves. This then means that we can eliminate the $1,000 to $1,500 charge that the mechanic applies every time he removes the valve cover.
Common Rail Fuel Injection. This is a term we hear a lot lately and while it isn’t limited to Volvo Penta it does mean that the engine will be operating quieter, smoke free, and is provided with a wider opportunity to comply with cleaner emission standards. In the rail, fuel is always available for the injectors, which feed the cylinders up to three times per stroke.
Fuel is pulled from the ship’s fuel filter (A) to the fine filter (B) on the engine by a vacuum created by the high-pressure fuel pump (C). The ECU or Electronic Control Unit (D) controls the fuel fed to the injectors based on several parameters, such as throttle position and temperature. The common rail (E) is fitted with a sensor to provide the ECU with information on the actual rail pressure. Then the fuel passes to the injectors (G) that are fired from the ECU.
Double Overhead Cam. This means less maintenance, and since there are no push rods, cam followers or rocker mechanisms, there are significantly fewer parts needed, and therefore fewer moving parts to wear.
Size Matters. The D6 uses seawater to manage the oil cooler, aftercooler and fuel cooler. This allows for a significantly smaller heat exchanger to cool the engine and therefore a smaller engine. That means that the D6 is sized to fit into a more broad range of engine compartments.
The D6 is sized to fit into a broad range of engine compartments, regardless of the drive systems utilized.
Ease of Maintenance
The technical side of an engine will only matter so much to an end user. Things like “common rail fuel injection” and “7 bearing camshaft” simply aren’t pretty. But what does matter is how things work when an end user gets his or her hands on them. Here are some key points that we find attractive in the D6-370.
Easy to Access Water Strainer. The water strainer is right at the front top of the engine making easy work of change-outs. There’s even a sight glass at the top for a clear view of the water flow inside.
Easy to Access Fuel Filter. Just behind the water strainer is the fuel filter. This is intended to be a secondary filter, the primary being installed on the boat. It’s equally easy to access as the water and for dealing with air in the system, there’s a priming pump right on top.
Dipstick. This is topped in a red handle for clear visibility and the stick itself is round so it doesn’t matter which way it goes back into the tube.
Aux Stop. Right at the top of the maintenance area is an aux stop button to electronically kill the engine. This is an invaluable tool when things might go wrong.
Primary and Secondary Oil Filter. Also right nearby are the two oil filters. These are cartridge type filters and “eco-friendly” as they contain no metal components and are easily recycled. The D6 holds 5.28-gallons (20 L) of oil including what is in the filters. It holds 4.36-gallons (16.5 L), excluding filters.
Coolant and Oil Fill. These are easily accessible as well as being located right on top of the engine.
Built for Varying Applications
Volvo Penta has a long history of matching engine performance to propulsion choices. Such is the case with the D6-370. Choose this engine regardless of whether the drive is inboard, sterndrive, or IPS pods.
The D6 is available in an inboard application with an electronically controlled reverse gear or V-drive. The high torque levels that make it so popular with the outdrive and pod applications are especially appealing in both single and twin inboard uses. Volvo Penta produces its own line of hydraulically shifted transmissions, purpose matched to the power of the D6. It utilizes beveled gear technology for operational reliability, and smooth running at all speeds. The 8-degree down angle also serves to optimize the match to inboard operations providing minimal shaft angle. The electric shifting via electromagnetic valve allows the D6 to take full advantage of the EVC system.
Diesel engines coupled to sterndrives are one of Volvo Penta’s most important product areas. Volvo Penta has optimized the D6-370 to operate with DPH drives, which have been modified for higher output. The results are excellent in both twin and single engine applications.
Volvo Penta’s Aquamatic drives are well regarded for their high efficiency, robust design, power steering and high power. Counter rotating bronze propellers are specially developed for the drive. Drives come fully equipped with hydraulic X-act steering with external steering cylinders. The exhaust system and seawater intakes are integrated into the drives.
The drives have a 50-degree maximum tilt angle and a built-in kick-up function to reduce damage in the event of a drive strike.
Volvo Penta’s IPS (Inboard Performance System) has revolutionized boating in so many ways. Today we are actually seeing manufacturers building boats with hull designs specifically engineered around this popular propulsion system. The model designators denote the level of power realized by this drive system, far above the actual horsepower of the engine itself. For example, the D6-370 is used in the IPS500 system and the 500 refers to the fact that the power output is largely the same as if a standard propulsion system were used with a 500-hp engine.
The D6 is available with a wide range of accessories thanks to the EVC controls. Here are just some of the features available.
Powertrim Assistant. Naturally, this will be specific to the Aquamatic range. Powertrim Assistant automatically trims the outdrive to provide the boat with the best trim angle for safety, comfort, and range. The outdrive is trimmed on five different axes which are preset against a given engine speed. For example, during acceleration, the drive is trimmed to the minimum so that the boat quickly starts planing and then trim is gradually increased to five, the boat’s best and most fuel-efficient trim angle.
Cruise Assist. Just push the Cruise Assist button and then the boat is basically in cruise control mode, just as with the car. But we know… you don’t have to keep your hands on the throttles like the car’s gas pedal. But we do want to make small, incremental adjustments to the speed like in the car. At the front of the engine controls is a small rocker that adds or subtracts 50 rpm at the touch of a button. Great feature to have when in no wake areas or making minor adjustments to accommodate varying sea states.
Single Lever. Push this button and the multiple engines can be operated with a single lever.
Joystick Operations. Whether sterndrives or IPS, there are joysticks available to ease the problematic docking situations. The shifts need to be in neutral and then the joystick physically engaged for the stick to work. This is an important safety feature and eliminates the concern of accidently “bumping” into the joystick when the engines are in neutral. This is also a good time to use the low speed mode for gentle approaches. Use the hi-power mode to add controllability in a stiff crosswind or heavy current.
The EVC Display. This is a great way to get in touch with your engines operations. Selectable screens and data give a complete picture of how things are operating, how the temperatures and pressures are, and our favorite…The current fuel flow and average fuel burns.
We’ve tested several boats with the D6-370, but it’s a rare boat that has this as a single engine application and we’ve tested a grand total of zero with inboard applications. Now that has more to do with the market segment of the boats tested favoring sterndrives rather than reflecting the engine itself. So as for twins, let’s take a look at how they performed, first with sterndrives.
Formula 400 Super Sport.
This is a boat with a test weight of 18,575 lbs. (8,425 kg). She had a top speed of 47.2 mph (76 kph) and a best cruise reached at 2500 rpm of 28.8 mph (46.3 kph). At that best cruise, the 400 SS was burning 19 gph (71.9 lph) for a range of 341 miles (549 km).
Formula 400 Super Sport test results.
Cruisers Yachts 41 Cantius
In this instance, we had a boat with a test weight of 26,295 lbs. (11,927 kg). She reached a top speed of 40.4 mph at 3570 rpm. At that speed we were burning 41 gph for a range of 231 nm. Best cruise came in at 2800 rpm with a 27.5 mph speed, a 24 gph fuel burn, and a range of 268.9 nautical miles.
Cruisers Yachts 41 Cantius test results.
Beneteau Gran Turismo 44
This boat presented a test weight of 23,311 lbs. (10,573 kg). She reached a top speed of 37.9 mph at 3450 rpm. At that speed we were burning 39.9 gph (151 lph) for a range of 158 nm. Best cruise was found to be at 3000 rpm and 31.3 mph. Now we had a fuel burn of 27 gph (102.28 lph) for a range of 192 nm.
Beneteau Gran Turismo 44 test results.
So from this we have a good cross-section of boats with an average test weight of 22,727 lbs. (10,308 kg). The average top speed was 42 mph with a fuel burn of 41 gph (155 lph). In fact, nearly all of the boats tested had a fuel burn of 41 gph, except for the Gran Turismo 44 that topped out at 39.9 gph (151 lph). Average cruise speed was 29 mph with a fuel burn of 23 gph (87 lph). Now let’s compare some figures with the IPS application.
Formula 40 PC
This boat had a test weight of 23,797 lbs. (10,794 kg). She reaches a top speed of 42 mph while burning 41 gph. Best cruise came in at 34.3 mph and 28.6 gph.
Formula 40 PC test results.
Cruisers Yachts 45 Cantius
This boat had a test weight of 30,936 lbs. (14,032 kg). In this instance, we hit a maximum rpm of 3630 in 42 seconds, where we saw the speedo read 31.7 mph or 27.54 knots. We recorded our optimal cruising speed at 24 mph, with a range of 279 miles turning the Volvo Pentas at 3100 rpm, burning a total of 28 gph.
Cruisers Yachts 45 Cantius test results.
Well here things are a little less dramatic at the top end. Now the average of our three boats is 25,242 lbs. (11,449 kg), so clearly the IPS benefits is leaning towards heavier boats. As such the average top end speed is a bit lower at 38 mph. However, the fuel burn is dead on at 41 gph (155 L) across the board. Best cruise averages out to 29 mph, 2.1 faster than with outdrives with the increased weight. Now however, the fuel burn is higher at an average of 27 gph (102 lph).
There’s little doubt that the Volvo Penta D6-370 performs well in both the sterndrive and IPS applications and we have little doubt that it will do the same in an inboard as well. There are a number of things that we like about the D6-370 but top of the list has to be that it was specifically designed for the marine environment, unlike most of the diesels on the market that were re-purposed from trucks or tractors. This is one reason why it is built to the size parameters that is making it fit into a broad section of engine rooms. There’s also a comfort level in all the components, from the engine itself to the drives, being made by a single company. If something goes wrong, there’s no finger pointing as to who is to blame. And Volvo Penta stands behind its products.