Marine Link
Monday, November 20, 2017

Powerful Additions

November 12, 1999

After success with six John Deere marine engines, a charter fisherman adds four new PowerTech 12.5 L engines to his fleet. Steve Tomeny can't get enough of a good thing. Neither can his customers who come back to Fourchon, La., to sport fish for red snapper, king mackerel, and tuna on his John Deere-powered charter boats. In 1997, two of Tomeny's three charter boats, Louisiana and Gulf of Mexico, featured twin 300 hp 6076AFM marine diesels. His third, Southerner, was powered by twin 460-hp V12 engines of another brand. Because the hulls on all three boats were identical, Tomeny was able to make some interesting comparisons of performance and efficiency - comparisons that eventually resulted in the purchase of four 450 hp John Deere PowerTech 6125AFM engines for his boats. Tomeny first repowered Southerner with twin PowerTech 12.5 L marine engines. Using the same four-bladed prop and Twin Disc 514 transmission used with the V12, newly repowered Southerner picked up the same load as before, yet burns 20 percent less fuel, explains Tomeny. "We're using 150 gallons per day, compared with 200 gallons with the V12s. We get an extra day of fishing out of the same amount of fuel." One of the main reasons for this exceptional fuel economy is John Deere's use of a full-authority electronic-engine-control unit and electronic-unit injectors. The design raises injection pressures 50 percent over mechanical fuel systems, provides variable timing, and better control of the start of injection. Diagnostic gauges on the PowerTech 12.5 L engine provides Tomeny with an automatic reading of his fuel use. Knowing the rate of fuel the engines are burning at various engine speeds helps him maximize fuel efficiency. Also factored is the "percent load" of the engine under various weights and speeds. "Balancing the engine speed, cruising speed, and percent load helps me determine the most optimum, economical speed," explains Tomeny. "It also helped me determine the right prop size and pitch." Since the switch, Tomeny says the boat achieved some performance gain, because the John Deere engines weigh considerably less than the V12s. Tomeny says the new engines are also quieter than the previous engines. "The Deere engines are much quieter out on the deck while we're fishing," he says, "and we're using essentially the same muffler system as before." Customers enjoy their fishing experience on the three boats so much Tomeny recently added a fourth vessel, Caribbean Sea, also powered with twin PowerTech 12.5 L engines. "It's the quietest boat that I have," says Tomeny. "We've noticed how clean these engines are; you can't make them smoke," relates Tomeny. "Caribbean Sea has been operating since June and had one day off. The exhaust pipes are white and clean on the inside. And on Southerner, people used to blame diesel smoke for their sea sickness. Now they'll have to blame it on something else." All four charter boats are also equipped with John Deere-powered gen sets, which power the air conditioners, livewells, lights, microwaves, coffee pots, kitchen sinks, and hot-water heaters. The generators turn at 1,200 rpm and produce 20 kW. One engine, a 4239D, has accumulated 23,000 hours. "The engine has spent 10 years in a salt-water environment, and I still haven't had to rebuild it," states Tomeny.
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