It’s not uncommon to repower older boats, especially those built 86 years ago.
But replacing an older diesel engine with brand new electric motors — electric motors powered by batteries? That may be about as uncommon as it gets, at least at the moment.
But this is the case for Tender 4, an old tug with two new EP-10000 electric motors from Elco Motor Yachts in Athens, N.Y. The 40-footer is working as a dredge tender on the Erie Canal for the New York State Canal Corp. With its new motors, the Tender 4 has been maneuvering dredges and dredge barges on the canal since June 17, according to Joe Fleming, Elco’s chief engineer.
The Canal Corp., a subsidiary of the New York State Thruway Authority, oversees and maintains New York’s canal system. It is comparing the performance and maintenance costs of the twin Elcos with the engine that had been in the boat, a 175-hp Detroit Diesel 6-71. Early results show they are “delivering 15 percent more horsepower to the shaft” than the Detroit, and “they drive the tug to its maximum hull speed.” said Fleming.
Then there’s the obvious working benefit to the crew. Asked what the biggest difference was between the electric motors and diesel engine, “the crew said there was no smoke, you can have a conversation and there is no vibration. The work day is a lot better because of the lack of vibration,” said Dean Heinemann, Elco’s director of sales.
And come this winter, the electric motors won’t have to be winterized, and any periodic maintenance that’s necessary with a diesel simply isn’t required.
STRAIGHTFORWARD PROCESS
Replacing the 6-71 Detroit with two Elco electric motors, each generating about the equivalent of 100 hp, was a fairly simple and straightforward process.
“We designed the electric assembly for bolt-for-bolt drop-in replacement for the Detroit Diesel,” Fleming said. “We used existing engine stringers and coupled up to the existing shaft.” The electric motors were set up in tandem within a framework that was bolted to the stringers.
Of course there’s no marine gear, as that’s not required with the electric motors. However, the same 33"-dia. prop that was used with the Detroit Diesel was retained, making for a better direct comparison between the diesel and the electric motors.
In the tug’s engine room, the two Elco motors take up about 30% less space than the old diesel engine. “There’s less volume, less length, less width,” said Fleming. The electric motors also weigh less, 740 lbs. per engine (1,480 lbs. total) compared to 2,190 lbs. for the Detroit 6-71. The frame the Elco EP 10000 motors are mounted on added just over 200 lbs.
Though the notion of an electric motor might conjure up a nightmarish wiring scenario, it’s basically a plug-and-play installation. “You don’t have to do any wiring except for the batteries. It reduces the chance of someone getting frustrated and getting it wired wrong,” said Heinemann.
Helm station controls come with the electric motors, along with a 15' cable that runs from the motors to the helm station. If that’s not long enough, several can be plugged into each other, up to about 75 feet.
The 36 batteries for the New York canal tug are absorbed glass mat batteries — half on one side of the engine room, half on the other. The sealed batteries use advanced lead-acid technology. As the name indicates, the electrolyte is contained within the glass mats, which are between the plates. Even if a hole is punched in one of the batteries nothing will run out. The AGM batteries also have a low discharge rate, about 1% a month, Fleming said.
The decision to go with 36 batteries was made “after looking at data taken on what a worse-case-condition work day was with that tender,” said Fleming. “It came out to be about 55,000 watts or 55-kW hours of work. We put 65-kW hours in rather than 55.”
Finding a place for the 36 batteries in the engine room wasn’t an issue. The batteries occupy an area of the engine room that wasn’t being utilized and their weight isn’t a problem.
In fact, even after the batteries were installed, and by not having to carry fuel for the heavier diesel, the tender was somewhat light in the stern. So the stern fuel tank was left in place. “The tank was cleaned out and used for water ballast,” said Fleming.
He estimates it probably costs only about $5 to $6 a day to recharge the batteries with shoreside power.
What did it cost to replace the Detroit Diesel 6-71? The EP-10000 electric motors are priced at $21,000 each and the 36 batteries come in at about $10,000. Fleming expects the batteries to last at least eight years. By then he figures the price of batteries will have dropped appreciably while they will provide several times the energy.
Fleming cited a 2013 article in The Economist (“The Future of Energy; Batteries Included?”) that reported on a group working at the Joint Center for Energy Storage Research in Lemont, Ill. Their goal, he said, is to make batteries five times more powerful and five times cheaper in five years.
Fleming said that the dredge tender operating on the Erie Canal with the two Elco electric motors and 36 batteries runs all day on a single charge. “If they do what they say they will, you could put new batteries in and it could run almost a week without recharging.”
The 40' dredge tender isn’t the only workboat powered with Elco Motor Yacht’s electric motors. A 66-passenger water taxi in Fort Lauderdale, Fla., uses Elco motors for propulsion, as does a 66-passenger boat for the Dorset Heritage Museum in Dorset, Ontario. The Fort Lauderdale company is in the process of powering another boat with electric motors, said Fleming.
Fleming recently worked up an application for a Canadian company that would operate a 60' catamaran passenger boat with an EP-10000 in each hull. The company wanted to know how much it would cost to recharge the batteries each day.
He gave them figures for operating at different speeds. “The worst case speed was at seven to eight knots. It would cost them 11 cents per kilowatt-hour, or roughly seven dollars a day to refuel the boat. How can you even touch that with gasoline or diesel?” asked Fleming.
A logging company has also talked with Elco about powering its small tugs with the electric motors. They are especially interested in electric motors for environmental reasons.
“They are logging and doing work in protected waters where they will be penalized if they have any kind of oil spill, so they are looking real hard at electric power,” Fleming said.
