Electric powertrain supplier, Arc, Los Angeles, Calif., has begun engineering a battery-electric conversion of Harbor Sentinel, a 50' harbor tug owned and operated by Pacific Maritime Group (PMG), Long Beach, Calif.
The project will replace the tug’s twin diesel engines with an electric Arc powertrain. Glosten, Seattle, is leading vessel engineering. Following commissioning, the tug will return to work from PMG’s Long Beach terminal for a 12-month demonstration.
Funding comes from the Port of Long Beach’s Technology Advancement Program (TAP) and SWIFT Program, along with a Volkswagen Environmental Mitigation Trust grant administered by the Bay Area Air Quality Management District.
Harbor Sentinel joined PMG’s harbor fleet in 2023 and moves barges and supports construction and shipyard operations. Its existing propulsion plant consists of two Cummins KT19 diesel engines producing a combined 950 hp. The tug carries 8,900 gals. of fuel.
The conversion will include structural changes as well as new propulsion equipment. PMG will widen the tug by 3.5' and build a new deck, midbody and pilothouse using its in-house capabilities.
Glosten completed a feasibility study and hull scan before engineering began. The firm is now adapting the vessel and designing onboard systems to meet applicable Coast Guard Subchapter M requirements.
The electric powertrain will include a battery bank targeting 2 MWh of usable energy, electric motors and drivetrain, power electronics to serve existing AC equipment, updated helm controls and captain displays, and onboard charging equipment with a DC fast-charge inlet. Telematics will provide around-the-clock remote monitoring, Arc said.
Arc said it will integrate, commission and test the system and prepare technical documentation for Coast Guard review of its equipment and components. The company will also provide on-site and remote support to PMG’s crew after the tug returns to service.
“In pursuing this conversion, we want to see exactly how Arc's powertrain handles the rigors of our Long Beach operations,” said Grant Westmorland, PMG’s CEO. “We are eager to measure the real-world impact on fuel savings, maintenance downtime, and operational torque.”
Westmorland said the demonstration will help PMG evaluate electric and hybrid propulsion for other vessels in its fleet.
The Port of Long Beach’s TAP supports demonstrations of emerging technologies on working port equipment under the San Pedro Bay Ports Clean Air Action Plan. During the demonstration, Arc will collect performance, operating and charging data, submit quarterly reports to the port, and prepare a final report evaluating the technology and its potential for broader commercial use.
The project adds a conversion to Arc’s commercial tug work, which also includes supplying and integrating battery and battery-management systems for eight electric ship-assist tugs under construction at Snow & Co., Seattle, for Curtin Maritime, Long Beach.
Snow & Co. began sea trials in November on the first 80'9"×42'3" tug, Tuuli C. The vessel has two 2,000-hp Schottel L-drive propulsion units and a 6-MWh lithium-iron-phosphate battery system. Its propulsion plant is designed to deliver more than 4,000 hp and 55 short tons of bollard pull.
The eight-tug program, announced in September 2025, is valued at approximately $160 million.
