When Is a Tug Too Old to Repower? Inside the $5M vs $20M Decision
With new ship-assist tug prices pushing toward $20 million, operators are taking another look at older hulls. One prominent U.S. operator says approximately $5 million can potentially buy new engines and Z-drives instead. The savings are enormous — but only if the old tug is worth saving.
The arithmetic is almost irresistible. Spend roughly $20 million for a new ship-assist tug—or take a hull the company already owns and put about $5 million into modern engines and drives. On paper, the repower starts with a $15 million advantage before the first line is thrown. But tugboats are not pickup trucks. Once stability, hull condition, machinery space, emissions equipment, downtime, financing, maintenance and future bollard-pull requirements enter the calculation, the cheapest project on day one is not always the cheapest tug ten years later.
$20 million new. Roughly $5 million to modernize the right old tug.
The comparison comes from Steve Shaver, president of Portland-based Shaver Transportation, in WorkBoat’s October 2026 tug-market report. Shaver said new ship-assist construction is approaching $20 million, while an older vessel may be modernized with new engines and new drives for approximately $5 million.
Shaver is not merely talking about repowers. It is doing two now.
Shaver told WorkBoat that two older vessels are currently being upgraded with Z-drives and Tier 4 engines.
That matters because this is an operator that simultaneously owns modern high-capability vessels. Its fleet includes Samantha S, with 8,400 hp and more than 100 tons of bollard pull, and the newer Heather S, rated at 7,000 hp and about 100 tons of pull.
In other words, the decision is not ideological. Shaver builds new where new capability is required and modernizes older hulls where the underlying platform still makes economic sense.
The newbuild in Shaver’s example costs roughly four times as much as the repower. But the two projects do not necessarily produce identical tugs. A new vessel can be optimized from the first plate for horsepower, beam, bollard pull, winch loads, escort forces, emissions equipment, crew spaces and future contracts. A repower has to live inside geometry selected decades earlier.
There are a lot of older U.S. towing vessels with useful steel still in them
The inspected U.S. towing fleet is old.
Coast Guard data for 2024 counted 4,927 inspected towing vessels and put their average age at approximately 35 years. That does not mean a 35-year-old tug is worn out. Commercial vessels can receive new engines, electronics, steel, wiring, piping, winches and propulsion equipment repeatedly over their lives. It does mean operators across the country regularly face the same question: how much new money should be put into an old hull?
A good hull can be an enormously valuable piece of already-paid-for infrastructure
When a tug already fits its harbor, passes structural inspection and performs the mission customers require, replacing the machinery instead of the vessel can avoid millions of dollars of steelwork, outfitting, accommodations and newbuild financing.
Existing hull
The operator does not pay again for every frame, bulkhead, deck and tank that remains structurally useful.
Known behavior
Captains already know how the vessel handles, where it works best and how it behaves in local winds, currents and berths.
Modern propulsion
New engines and Z-drives can transform maneuverability and restore machinery reliability without constructing an entirely new vessel.
Lower borrowing need
Financing $5 million instead of $20 million produces a dramatically smaller annual debt-service burden.
Modern emissions
Repowering can replace legacy engines with modern EPA-compliant equipment when a technically feasible installation exists.
Faster capital recovery
A smaller investment requires less incremental earnings from the tug to produce an acceptable return.
The company’s own history helps explain why it is comfortable spending on old steel
Shaver reports that it repowered twelve vessels during an earlier fleet-modernization period. The tug Portland provides an especially useful example of why some older platforms survive.
Portland: roughly 40 years old and still worth upgrading
Portland entered service in 1981 as an early U.S. Z-drive tractor tug. Kongsberg later replaced its original propulsion units with modern US205 thrusters while retaining the same engine power. The supplier described the upgrade as reinvigorating the approximately 40-year-old ship-assist tug for decades of further operation.
Newbuilds still have a place
Shaver has simultaneously invested in new high-powered tractor tugs such as Samantha S and Heather S. That is an important distinction: a successful repower strategy does not mean avoiding new construction. It means buying new capability only when the mission justifies the extra capital.
The first question isn’t “How much will the engines cost?” It is “Can this hull take them?”
A conventional tug cannot automatically become an ASD tug.
Harbor Docking & Towing president John Buchanan told WorkBoat that some conventional twin-screw vessels simply do not have the beam, draft or stability characteristics needed for an effective azimuth-drive conversion. Installing propulsion equipment that physically fits is not enough; the completed tug still has to behave safely under ship-assist loads.
Ultrasonic steel measurements, wastage, cracking, corrosion and historic repair quality determine whether the remaining structure deserves another major investment.
Z-drives, foundations and new machinery alter weight and center of gravity. Adequate transverse stability cannot be assumed.
Tier 4 installations may require SCR equipment, dosing hardware, exhaust changes and diesel-exhaust-fluid storage that the original designer never anticipated.
Engines are only part of the job. Pumps, generators, wiring, controls, ventilation, exhaust and cooling systems may need significant modification.
More propulsion does not automatically make the deck machinery suitable for higher-load escort or ship-assist work.
A beautifully repowered 55-ton tug is still a 55-ton-class platform if the next customer requires 90 or 100 tons.
Modern emissions equipment can turn machinery-space geometry into the deciding factor
An engineering study prepared for the California Air Resources Board provides useful historical perspective. For a representative 100-foot ship-assist tug with twin 3,425-hp engines and existing azimuth propulsion, the study estimated roughly $2.8 million in capital and installation cost for a Tier 4 main-engine repower. That was a 2019 estimate and did not represent the broader new-engine-plus-new-drive project Shaver is discussing today.
What remains highly relevant is the engineering lesson: even on a large tug, investigators had to find room for DEF tanks, SCR components, revised exhaust arrangements and structural modifications.
Space can become more valuable than horsepower.
The recent Edith Foss Tier 4 repower illustrates the problem. The 77-foot tug was built in 1980 and had virtually no unused machinery-room volume. Designers had to alter tank arrangements to create DEF storage, sacrificing some fuel capacity and performing new stability analysis. The project also experienced manufacturer delays that extended its schedule.
The $15 million purchase-price gap gets smaller—but it does not disappear easily
The following model is deliberately illustrative rather than a forecast for any specific tug. Its purpose is to show how the decision changes once financing, fuel, maintenance, downtime and residual value are put on the same page.
Illustrative base assumptions
| 10-Year Cash/Economic Item | New Tug | Repowered Tug | Difference |
|---|---|---|---|
| Purchase / project cost | $20.0M | $5.0M | $15.0M repower advantage |
| Annual loan payment* | ≈$2.28M | ≈$570K | ≈$1.71M/year |
| Total financed capital cash* | ≈$26.78M | ≈$6.70M | ≈$20.09M |
| 10-year fuel | $9.20M | $10.00M | $800K newbuild advantage |
| 10-year maintenance | $2.50M | $5.00M | $2.50M newbuild advantage |
| Illustrative downtime cost | $0.75M | $2.85M | $2.10M newbuild advantage |
| Residual value credit | −$10.0M | −$2.0M | $8.0M newbuild advantage |
| Illustrative 10-year economic cost | ≈$29.2M | ≈$22.5M | ≈$6.7M repower advantage |
*Illustration assumes 20% down, 80% financed, 7% annual interest and a 10-year amortization. Fuel, maintenance, downtime and residual values are scenario assumptions, not reported Shaver Transportation financial data.
In this particular illustrative scenario, the repower retains roughly a $6.7 million ten-year economic advantage. That means a newbuild would need to generate approximately $670,000 of additional annual economic contribution over ten years to close the gap. A higher-paying escort contract, fewer tugs required per ship, materially higher utilization or lower downtime could plausibly provide such value. If the new tug performs exactly the same commercial work as the repowered vessel, recovering the capital premium becomes much harder.
The expensive tug can be cheaper when the old hull prevents the operator from earning tomorrow’s revenue
The existing hull still fits the business
- Steel and structure have substantial remaining life.
- Beam, draft and stability support the desired propulsion system.
- The existing vessel already fits local berth and channel geometry.
- Current bollard-pull requirements are likely to remain adequate.
- The operator owns the vessel outright or has little remaining debt.
- Modern engines and drives can fit without extreme structural work.
- A lengthy newbuild wait would delay needed capability.
The mission has outgrown the old platform
- Customers increasingly require much greater bollard pull.
- Escort work demands hull forces an older design cannot produce safely.
- Tier 4 equipment cannot fit cleanly in the machinery spaces.
- Steel, piping, wiring and auxiliary systems also need major renewal.
- Crew accommodations or visibility are fundamentally inadequate.
- The new vessel could replace multiple older assets on certain jobs.
- Long-term contracts justify purpose-built capability.
A $5 million project can become an $8 million project one discovery at a time
Repower economics are unusually sensitive to scope creep because the shipyard is working around a structure it did not build and machinery arrangements drawn decades earlier. Opening the hull can expose costs that were difficult to price perfectly before demolition began.
Tank tops, foundations or framing that looked serviceable during preliminary inspection may need replacement once machinery is removed.
Modern electronically controlled engines and azimuth drives can force major upgrades to bridge controls, alarms, power distribution and wiring.
DEF, fuel or hydraulic tanks may need to move, changing endurance, trim and stability.
New engines and drives impose different weight, torque and structural loads than the equipment being removed.
Delivery delays for engines, drives, electronics or castings can keep a revenue-producing tug tied to the dock longer than planned.
Once a tug is opened up, owners often decide to renew generators, piping, HVAC, deck machinery, accommodations or electronics simultaneously.
Repower the hull when the hull still matches the next ten years of work—not simply because it survived the last thirty.
That distinction captures the economics better than age alone. A forty-year-old tug with good steel, appropriate dimensions, useful bollard pull and a strong local mission may be an excellent candidate for another machinery cycle. A twenty-five-year-old tug that cannot safely accept the required drives or winch loads may already be commercially obsolete.
The $20 million versus $5 million comparison therefore should not be read as “old boats are cheaper.” It should be read as a reminder that operators already own millions of dollars’ worth of hull, outfitting and vessel history—and sometimes the financially intelligent move is to keep that asset and replace only the technology that has become obsolete.
Research base
This report draws on WorkBoat’s October 2026 U.S. tug market report; Shaver Transportation fleet, history and shipyard information; Kongsberg Maritime’s documentation of Shaver propulsion upgrades; Caterpillar/Sterling Shipyard Tier 4 repower experience; U.S. EPA marine diesel standards; U.S. Coast Guard domestic fleet statistics; California Air Resources Board engineering analysis of Tier 4 commercial-harbor-craft repowers; and reporting concerning the Edith Foss modernization program. The $20 million and $5 million figures are individual operator examples and should not be interpreted as universal market quotations.
Newbuild or repower? Run the 10-year numbers.
Adjust the variables that can completely change the answer: project cost, financing, maintenance, fuel efficiency, downtime and residual value. The model compares economic cash cost over ten years.
