Yanmar Six

A Yanmar six grows legs

There's a cloud on the horizon for some of the better known diesel marine powerplant brands. And ironically, it's a product that boasts smoke-free performance as one of its virtues.

I'm talking about the new sterndrive version of the 1997-release Yanmar LP-series six-cylinder turbo-diesel. Available in 12-valve 250hp and four-valve per cylinder 300hp versions with a range of MerCruiser drives, the packages will be marketed Australia-wide by local Yanmar distributor Power Equipment Pty Ltd.

The new powerplants are the product of a five-year agreement between Yanmar and MerCruiser's parent company, Mercury Marine.

The agreement sees the power units assembled in Japan and the dedicated MerCruiser Bravo One, Two or Three drive units built in the USA. The units are then individually shipped to Yanmar distributors around the world.

It is the first time that MerCruiser has entered into such an agreement which speaks volumes for the faith the huge US corporation has in the project.

Given the Yanmar Diesel Engine Company's background, that faith appears well-placed. Established in 1912, Yanmar is among the world's largest producers of diesel engines. It's also credited with constructing the first 'small' diesel engine four decades after Rudolph Diesel invented the diesel concept. Small is a relative term when it comes to early diesels. Yanmar's landmark 1933 Model HB (H was for horizontal, B was the power rating used in the days of offset kerosene engines) weighed in at around 500kg and produced between five and six horsepower at a lazy 550-650rpm. Still, the watercooled powerplant was a fraction of the size of Herr Diesel's original three-metre high behemoth.

A company with a proud history, Yanmar's corporate obsession with perfecting the diesel concept has seen it adopt what it calls a unified production system. This system is unique in that Yanmar states it is the only volume manufacturer of diesel engines to construct all the attendent parts for engines. This includes precision pieces like fuel injectors and fuel pumps.

This policy has only recently been stretched to allow design input from outside the company. The LP-series engines are a case in point, as they are derived from the SOHC powerplant that powered the 80-series Toyota LandCruiser.

It was during the early 1990s collaboration between the two Japanese giants while constructing Yanmar's fully automated engine plant near Lake Biwa near Nagahama that this union blossomed.

At the time, Yanmar was busy planning the expansion of its marine engine range into the performance sector of the pleasure craft market. Though its 5.2lt LY-series dealt with the 315-350hp segment and the 3.5lt four-cylinder LH engines rated up to 230hp, the 250-300hp sector was unaddressed.

This was a lucrative sector in terms of both new installations and the repowering business.

In what amounted to a huge 'cultural' change for Yanmar, the decision was made to re-engineer the powerplant and take advantage of Toyota's even larger economies of scale. Thus, the LP-series Yanmar engine was born.

Today, redesigned OEshort' engines are manufactured and assembled to Yanmar's specifications by Toyota, before shipping to Yanmar for completion.

Launched in Australia in 1997 (also at the Sanctuary Cove show), the 6LP has already won over more than a few boat builders' hearts Down Under.

Quite apart from the performance claims for the powerplant, its size and weight, or rather lack thereof, make it stand out from the crowd.

According to Yanmar's figures, at 458kg (including ZF gearbox) it is 34% lighter than Perkins' M265 (265hp), 44% lighter than the Volvo TAMD63L (310hp) and 37% down on CAT's 300hp 3116. In installation envelope terms, the powerplant is up to 132% smaller than these competitors.

Performance-wise, the LPs are relatively high revving engines, producing their peak horsepower at 3800rpm in both rated versions. Yanmar points out that this ability to rev higher allows the use of smaller smoother running props in shaft installations.

Nevertheless, assuming that the powerplants are rev happy is wrong. According to published engine performance graphs, the DTE version of the powerplant produces near to peak power from 2700rpm through to the above-stated 3800rpm peak. The 24-valve STE plateaus at 3000rpm, giving a 800rpm range of maximum urge.

Torque-wise, published peaks are 650nm (478ft-lbs) at 2600rpm in the case of the DTE and an even 700nm (515ft-lbs) from 2500-3000rpm for the STE.

It is our experience of the (shaft-drive) 6LP-STE that the belt-driven SOHC powerplant also boasts near-automotive levels of refinement in terms of noise, vibration and emissions.

If you get the message that we're talking about an impressive powerplant, you're on the right course.

All of the 'pluses' noted above make the LP-series ideally suited to be mated with a sterndrive unit. In fact, Yanmar is quietly confident that the overall performance versus size/weight equation of the new packages will have boat manufacturers here and abroad re-evaluating their use and choice of sterndrives in boats right up to the 10m mark.

A local example of this is sportsfishing boat specialist Black Watch. According to the Gold Coast-based manufacturer, the new Yanmar is ideally suited to its 26 available in flybridge, targa, and soon a centre cabin version. Unlike current installations, the DTZE and STZE will allow the 26-footer to feature a flat cockpit floor an important consideration in a sportsfisher.

It goes without saying that the repower market is also wide open to the new mills. Light-weight petrol performance with diesel economy is a powerful attraction of these powerplants.

In fact, the major hurdle the new units face Down Under would appear to be the continued Aussie ambivalence to sterndrive-equipped boats.

Though the days of rampant corrosion, myriad niggling problems and high maintenance costs are well gone, most Australian boaties are still able (and willing) to quote horror stories about sterndrives.

Given the reliability record of modern sterndrives, especially MerCruiser products, that's more the pity. Early indications are that if ever there was a pre-package drive unit that deserved to succeed, it's this one.