Crowley, Jacksonville, Fla., has repowered two of its escort/ship assist tractor tugs — Master and Leader — both measuring 103'x36'x15'. Crowley officials said the repowers are major investments, typically exceeding $1 million.
While not part of routine maintenance, repowers are essential during a tugboat’s 30- to 40-year lifespan to extend service life, comply with evolving emissions regulations, and address engine wear that can impact performance and reliability.
The Master, delivered in April 1998, was the first of six 4,800-hp tractor tugs that Nichols Brothers Boat Builders, Freeland, Wash., built for Crowley’s Vessel Management Service (VMS) in 1998 and 1999. The tractor tugs were originally designed by Guido Perla and Associates, Seattle, and VMS and built by Nichols Brothers. The Leader was delivered in December 1998.
Crowley’s Harbor-class tugs were built specifically for ship assist and escort duties and feature a hydrofoil shaped skeg meant to provide improved steering, control, and seakeeping. The design allows the vessel to run at high speeds in the skeg-first direction. Additionally, the hydrodynamics of the hull result in increased tons of steering, and braking force, which are available to assist or control a vessel at higher speeds.
To uphold its commitment to safety, efficiency, and environmental responsibility across its ship assist and escort fleet, Crowley initiated repower projects for the two tugs, turning to its in-house engineering services team to oversee the projects, leveraging their expertise from managing hundreds of newbuilds and retrofits across the maritime industry.
Consequently, the Master and Leader were successfully repowered, achieving improved vessel performance, sustainability, and regulatory compliance, according to Crowley officials.
The repowering focused on two specific areas — engine replacement using Tier 4-compliant diesel engines and auxiliary systems that enhanced the cooling and exhaust systems to align with the new engines.
Crowley used Caterpillar 3512E diesels producing 2,549 hp at 1,800 rpm to repower the tugs. The original engines were Cat 3516B diesels developing 2,400 hp at 1,785 rpm.
The repower tugs have Voith drive units, controls, and steering system. Dive units and engines are connected through Falk 12x7Z1-S marine gear with 1.828:1 reduction ratios. The original engines connected to Voith Schneider 28GII/210 cycloidal drive units via Falk 721-S gears with 1.828:1 reduction ratios.
Ship’s service power for the repowers are the responsibility of two John Deere 6068 gensets. Originally, the electrical power came from twin Cat 3304 DIT generators providing a total of 210-kW of electricity for onboard systems.
Tankage for the repowered tugs include 34,114 gals. of fuel; 8,316 gals. fresh water; and 2,212 gals. lube oil.
The repowered tugs are ABS loadine certified.
