Invader-class refurbishment finished at North Florida Shipyards

The last Invader-class tugboat to be refurbished as part of a four-year shipyard investment by Crowley Maritime Corp. has returned to her home port in Jacksonville, Fla.

The 7,200-hp tug Sentry was delivered by North Florida Shipyards in May and quickly put back to work towing 730-foot triple-decker container barges from Jacksonville to San Juan, Puerto Rico, for Crowley Liner Services.

Crowley’s entire fleet of 25 Invader-class tugs, all built in the 1970s, underwent complete refurbishment of engines, systems and interior spaces in the upgrade program designed to give each tug an additional 15 years of service life. The last 11 refurbishment jobs were done at North Florida Shipyard in Jacksonville. The Invader tugs, designed by naval architect Phillip Spaulding of Seattle, were similar to the company’s Sea Swift class except for their larger, turbocharged 20-cylinder EMD 645 E-5-series engines. The sleek, traditional-looking tugs can generate 150,000 pounds of bollard pull.

These tugs are named after the original Invader, launched from J. Ray McDermott Shipyard of Morgan City, La., in 1974. By the time 24 more of these low-slung, deep-draft offshore workhorses were completed a few years later, they gave Crowley the most impressive fleet of high-horsepower tugs working in American waters. It is a testament to both the Spaulding design and the company that operates them that the fleet is still intact and still setting the standard, in many ways, for large offshore tugboats.

By Professional Mariner Staff