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Replacing the Engines

Contemplating a new powerplant for your boat? Join us as we begin repowering the 1996 Grand Banks motoryacht we’re totally rehabilitating—and we mean totally—way down south in the Virgin Islands.

Our charterboat guy Tommy McCoy’s got a practical, salty streak to him. And his decision to repower Arawak, a 1996 Grand Banks motoryacht that’s been in his fleet for quite some time now, was a practical one. “In a nutshell,” he says, “the financial side of going with new engines outweighs the option of rebuilding the old ones. And I gotta also add that the conversion from Caterpillar V-8s to a narrower Yanmar inline-6 configuration is rather exciting to me. The amount of space I’m going to gain in Arawak’s engine room, both inboard and outboard, is gonna be pretty grand the way I got it figured.”

McCoy’s approach to the not insignificant task he’s just embarked upon, especially in terms of the first point he makes, pretty much jibes with the advice he’s getting from the folks that are giving him significant support, both at Yanmar USA and, for the repower itself, at Mastry Engine Center in St. Petersburg, Florida, a Yanmar company as well as Yanmar’s primary repower specialist in the southeastern United States, the Bahamas, and the Caribbean.

old engine

“While rebuilding a couple of existing engines does often pose fewer challenges,” argues Mastry’s general manager Kevin Carlan, “installing new products on a boat of this type will often provide long-term economic as well as other advantages. Think about it. There are a whole lot of older parts on older engines, including alternators, starters, and water pumps, and they’ll most likely be retained after a rebuild is completed. And hey, older parts are going to have an uncertain life expectancy when compared to new powerplants. And what’s more, remember that new engines are going to have a very valuable, very inclusive manufacturer’s warranty that the rebuilds are not going to have.”

Of course, there are any number of things to think about at the start of any repower project, the majority of them going well beyond the initial, repower vs. rebuild issue. For instance, the next step for McCoy, once he’d decided to repower with the Yanmar brand  (based primarily on the company’s reputation for long-term reliability and service), was figuring out precisely which engine model to go with, a decision that was fairly easy for him to make, the way things turned out.

new engine

“I’ve never been one to try and defy hull speed on a trawler,” he says. “I’m perfectly comfortable with speeds between 7 and 9 knots over long distances. So coming up with the appropriate engine model wasn’t a tough job. In fact, converting from 210-horsepower Cats to 220-horsepower Yanmar 6BY3-220s was a flat-out no brainer.”

Settling on how much horsepower to shoot for is not always as straightforward as it was for McCoy, though.  While most displacement boats, as well as many others vessels with semi-displacement-type hull forms, are indeed best served with a new powerplant that closely matches the original in terms of rated horsepower, planing watercraft, which are typically speedier and more weight-sensitive, may benefit greatly from a much more significant changeup. In fact, according to the repower gurus at Yanmar, today’s lighter engines often make it possible to install less powerful engines than the original ones while equaling and often exceeding existing performance. Moreover, engines that are similar in weight and size to the originals may provide considerably more power, thereby boosting both acceleration and top-end speed.

At present, McCoy is deep into the preparation stage of his project. So far, he’s removed one old engine from Arawak’s engine room and is starting to work on the second.  The extraction process is an interesting one and relies heavily on McCoy’s creative nature, which he’s successfully employed for years while running charter operations in the U.S. Virgins.

For starters, the old engine mounts are unbolted, the propshaft is de-coupled and pushed astern, and the gearbox, exhaust manifold, cooling tank, and heat exchangers are removed to lighten the load. Then an aluminum A-frame with a ball-bearing trolley is moved into place over the ER so that a slow but sure vertical lift can be facilitated. Next, thick planks are positioned on a slant, running from the edge of the ER’s access hatch up through the salon and out through the salon’s after window, which has been temporarily removed. Then finally, with an assist from a set of come-alongs and a chain fall (to longitudinally orient the engine with respect to the planks), the engine is pulled up the ramp and out onto the back deck where it is lifted off with a forklift.

engine add ons

“To give you a sense of the time involved,” says McCoy, “It took from ten to 12 hours to get the engine entirely out of the engine room and  put it down on the salon sole for a breather. Then to remove the engine entirely from the boat, I’d say it took an additional four or five hours. Hey, it’s not a horse race, you know. Nice and easy always seems to win the prize, at least on projects like this.”

Meanwhile, Yanmar is pretty deep into the project’s prep stage as well. At press time, a set of brand new Yanmar 6BY3-220s were being boxed up for shipment to Mastry’s repower shop in St. Pete, where they’ll undergo procedures the company is justly famed for, as well as highly experienced at. After all, getting new engines to fit into an old boat entails matching all sorts of new-engine-mounted paraphernalia—to do with fuel, cooling water, exhaust, electrics, and air supply—with what’s still onboard. And Mastry is especially good at easing this sometimes rather complicated linkup via a plethora of spacers, flex couplings, reducers, and other synergizing components that are custom fit to each particular engine for each particular application, whether the repower replaces old diesels or old gas engines with new.

“Mostly, we install the stuff here,” explains Mastry general manager Carlan, “so that things go smoother once the engines get to their destination. We’ve been at this sort of thing for a long time now—we generally know what may be needed on the other end.”

So anyway. We’ll report on further developments in McCoy’s repower project at, for sure. Besides being well on his way to having the second Cat extracted at this point, he’s also well on his way to disposing of several peripheral issues, one at least partly cosmetic. More to the point, Arawak’s engine room will receive a total “facelift” before the new engines arrive from Mastry, says McCoy, with paint and other products from Interlux and other manufacturers. “And I am totally hoping I can avoid replacing the fuel tanks,” he adds, eschewing, at least for the time being, a project that would undoubtedly add many hours and perhaps much heartache to his labors. A very practical point of view, but typical of McCoy.

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