YANMAR’s latest inboard diesel

A Common Rail

YANMAR’s latest inboard diesel is compact and powerful.

One of YANMAR’s initiatives is to “explore technologies that combine efficiency, high performance, and environmental friendliness” into its products, including recreational marine engines. Its been doing so since 1971 with the introduction of its first purpose-built engine for recreational use. Fifty years later, YANMAR debuted the 6LF series, a six-model lineup of common rail marine engines from 485 mhp to 550 mhp (478.3 hp to 542.4 hp). Installations of the new 6LF series began earlier this year, and the first one in Europe was a repower last August in a Magnum 40.

Environmentally Friendly

Keeping in line with YANMAR’s “environmental friendliness,” the 6LF line of marine engines meet EPA Tier 3 emission standards. The series also keeps in step with YANMAR’s “Best in Class” efforts for all its common rail marine diesel engines by making them fuel-efficient. Common rail engines are built with a direct fuel injection system that feeds solenoid (electromechanical) valves instead of a fuel pump feeding unit injectors that combine the injector nozzle and injection pump in a single component.

The 6LF engine “features YANMAR’s proprietary fuel mapping and a larger mixing elbow for reliable and consistent output performance,” says Jules Riegal of Saltwater Stone, YANMAR’s marketing firm. The YANMAR 6LF series and all its common rail engines minimize fuel consumption and optimize performance with precise, digitally controlled fuel injection that increases efficiency as well as reduces emissions and noise.

Electronic Control

Another aspect of YANMAR’s best-in-class efforts is interconnectivity. The engine is designed to integrate with the latest electronic components and multifunction displays for engine monitoring and control.

“It is custom engineered to offer direct connectivity to NMEA and J1939 CAN bus networks,” says Riegal. “It comes available with a number of standard and optional features, including single- and two-pole (12V/24V) installation, various ZF gears, and custom secondary alternator options to meet nearly any complex application.”

The 6LF series is operated by the VC20, YANMAR’s second-generation vessel control system. Based on the J1939 CAN bus system with a dedicated network to the engine, the system directs all engine and transmission functions, including joystick controls, and shows engine alarms and diagnostic codes in the display.

The control system also integrates with YANMAR’s complete lineup of common rail engines, ZF transmissions, and drives for sail, power, and light-duty commercial vessels to
55 feet.

Time to Repower

The compact and powerful 6LF series engines are a good choice when your boat is still comfortable but the engines have lost their efficiency. Old engines can lose horsepower, consume too much fuel, and require increased maintenance that makes for more downtime.

The Magnum Marine 40 was known for its speed and agility back in the ’80s and reached into the 60-mph range. It was a one-of-a-kind model, so it’s a keeper, but it had two 20-year-old mechanical 420-hp diesel engines and, over time, the performance didn’t compare with today’s engines. The boat was repowered with twin 6LF 530 engines along with new components, and the results were obvious: improved speed and fuel efficiency with low vibration and decreased engine noise.

There is the option to rebuild the engines, but YANMAR suggests that it might be worth the investment to repower if the rebuild costs 40 percent or more of the price to install new engines. Life expectancy, warranty, and the latest technology are also things to consider.

YANMAR’s 6LF series is available in three outputs: 485 mhp, 530 mhp, and 550 mhp, all with a 3,000 rpm rated speed. The inline, 4-stroke, 6-cylinder, water-cooled diesel has a number of accessory options along with a global service network. yanmar.com

-by Steve Davis

Keep an eye on your engine’s cooling system.

Recently I had both inboard diesel engines of the boat I was delivering dialed in at 2200 rpm and moving along at a comfortable speed. My feet were up, my back was settled into the pedestal chair, and I was enjoying the ride as I made my way to the marina at a slow bell when the starboard engine alarm went off. The rpms on the state-of-the-art, electronically controlled engine quickly went from 2200 to 1500 and then to complete shut down. Bringing both throttles back to neutral, I noted a spike on the digital temp gauge and instantly wondered what could have gone wrong from intake to exhaust and everything in between.

I checked the expansion tank’s coolant cap, water pump, the various hoses, clamps, and exhaust riser before taking a look at the raw water sea strainer. After unscrewing the lid, I detected bits and pieces of thin plastic.

I got away lucky on this one. The source of the problem was a small plastic bag. I shut off the thru-hull intake, removed the hose, checked the impeller, and cleared the residue. Problem solved—a much better outcome than a catastrophic engine failure. To keep your system running cool, let’s first look at the operation of an outboard engine.

“The cooling system is quite simple,” said Mike Nimmer, Mercury Marine’s product service manager. “Powered by an impeller in a water pump, raw water—whether it is salt, brackish, or fresh—comes in through the lower unit, is forced around the powerhead and then leaves the engine via the exhaust. No water coming out of the tell tale is a sure sign something is wrong.”

Much like my experience, the protocol on an outboard is first, when noticeable change in operating temperature comes into play, to shut down the engine. (With multiple engine configurations, when possible, get back to the dock before checking things out.) Lift the lower unit out of the water and check the intake port. If it is clogged or shows signs of debris, clear it. Lowering the engine back down and a quick start will confirm if that was the problem. “If not,” says Nimmer, “it’s time to have a look at the water pump and impeller.”

Be familiar with your engine manual and know the correct procedure for doing this kind of maintenance. “If you pull that impeller out, you’re most likely going to need to put in a new one so always carry the right spares,” Nimmer said. While impellers are quite robust, if you operate your engine(s) in areas of shallow water, this can often result in sand or other debris entering the system, so check yours on a regular basis. “If you store your engine over a season, put in a new one before you launch again,” suggests Nimmer. This is also a good time to check the seal on the water pump.

A problem with the engine’s thermostat and relief or bypass valve can also cause overheating. Pre-set to a factory determined setting, this device regulates water temperature to cool the engine, while keeping the proper pressure in the system for proper transfer of generated heat.

If any debris or corrosion is present, the thermostate should be swapped out. Your engine owner’s manual will detail this simple operation. “Never run your engine without its thermostat,” warns Nimmer. “It’s designed to protect and without it, severe damage can occur.” And regardless of what kind of water you boat in, Nimmer recommends you freshwater flush your engine after each use.

Inboard diesel or gasoline boats both have closed, expansion tank systems and raw water cooling with important maintenance items to be observed.

Know the proper operating temperatures of your coolant levels and manifold at various rpms. A difference of a few degrees can indicate trouble. Check with your owner’s manual for this information as well as your own daily maintenance log. (If you don’t keep one, now is a good time to start.)

Knowing the flow amount of your exhaust water is also key to confirm problems with your cooling system—as a boat operator, you should know this by sight. Should you see any restricted flow, shut the engine down and starting at the thru-hull, work your way through the system. A ruined impeller—a major cause in many cooling system problems—can send rubber pieces into the heat exchanger. If you run gasoline engines, you most likely have cast iron risers. As these are quite prone to corrosion in salt water, make checking them part of a seasonal inspection.

Besides the usual suspects such as the water pump, seal, belt, and impeller, follow the hoses, look at the clamps, and make sure the expansion tank cap is on properly. If this hasn’t been done in a while, take the fittings off the heat exchanger and check for clogs and marine growth. If any are present, clear things out with a thin wire brush. It is also a good idea to use an engine flushing product such as Barnacle Buster at least once a season. And use the correct antifreeze as per your engine manufacturer’s recommendations.

With cooling problems the heat generated can ultimately ruin an engine. Carry spare impellers, pre-cut hoses, clamps, the correct antifreeze, and the proper gaskets, grease, and tools aboard before setting out. I also like to have a full roll of self-fusing silicone tape in my toolbox—it can provide a great quick fix for a leaking hose until you get back to the dock. And don’t forget that all-important owner’s manual.

If you suspect something is wrong it’s time to shut it down. And if you’re not up to the task, get your marina manager on the phone or seek out a reputable mechanic to get the job done

By Ken Kreisler, Southern Boating Magazine December 2015

Tag: inboard diesel