Yanmar Marine extends its line of marine motors with the unveiling of a pair of marinized, BMW turbo diesels rated 220 and 260 horsepower. Stern drive and inbaord models are available. Both the 6BY220Z and the 6BY260Z are inline six-cylinder motors featuring common rail, direct injection with vertical injectors. Predictably firmware and electronics manage to finesse maximum horsepower per cubic inch and still turn in enviable fuel economy. Did I mention these engines are uncharacteristically quiet for a diesel? Further blasphemy, they don’t smoke. Another worthy item is the instrument panel that talks to the engines via CAN bus, displaying vital numbers on a multi function gauge

In Miami I tested the first one to hit the water, a 260 horsepower In-line six bolted up against to a MerCruiser Bravo Three stern drive. The platform was a Regal Commodore 2665, a 29 foot cruiser, a model that‘s been around for awhile.

The Yanmar marinized BMW is intercooled and turbocharged. That means a huge volume of cold, dense air (full of oxygen) is forced into the combustion chamber, building more torque than ought to be legal. So naturally acceleration comes on strong. Because it’s a common rail diesel, smoky exhaust is virtually eliminated, fuel economy is stellar and most of the characteristic diesel rattling has been silenced. A MerCruiser stern drive is an important part of the package. Spinning its twin, counter -rotating propellers, the Bravo Three drive leg amplifies engine performance by about 30 percent. That means perkier acceleration and greater mileage, when compared to a conventional single propeller stern drive. Twin wheels also grab the water better, improving maneuvering at all speeds and in both forward and reverse gears. In short, what we have here is a potent performer with impeccable handling manners. I also like the ample electrical output that comes standard.

On this boat, on this bright and shiny day, cruising speed (best mileage) was bracketed between 32 to 34 mph. We caution readers that this was a prototypical installation and performance numbers, while certainly impressive, will undoubtedly improve in production engines as fuel mapping and propeller sets are dialed in to the nth degree. Also important to note, in the interests of fair play we did not test sound levels. This for the simple reason the cockpit sole was not sound insulated. Recall the package was a prototype. Stay tuned for future tests conducted on production boats. © Copyright 2007  by Tim Banse

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Performance Numbers

Two thirds fuel load (50 gallons), no freshwater and six men on board. 85 degrees Light chop, light wind. Conducted on the waters of the Intracoastal waterway between Miami and Miami Beach.

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