Fleet renewal is becoming essential in today’s evolving small merchant vessel market. Many vessels are approaching the end of their operational life, and owners must now find flexible, future-ready solutions to meet tightening IMO and regional decarbonisation targets.
Wärtsilä supports small merchant ship owners commissioning new vessels – and the designers shaping them – with integrated propulsion and energy solutions that balance performance, compliance, and cost-efficiency.
Whether you're planning a newbuild or considering upgrades, Wärtsilä is your strategic partner for small merchant vessels.
It’s important to consider the vessel’s drive train, energy flows, and behaviour as a whole. A successful integration of the propulsion system into vessel design can bring great results – saving big on fuel. Watch this 2-minute video to learn more:
Tanker vessels operating on short sea routes must meet a range of operational requirements. They may be chartered on short-term agreements with different voyage distances, load conditions and sailing speeds.
It is critical to optimise a coastal tanker vessel’s CAPEX and OPEX to secure its competitiveness and profitability.
Vessel type: Coastal tankers
Typical size range: 3,000–15,000 dwt
Most optimal solutions:
Feeder vessels are typically small container vessels that transport containers from smaller hub ports to larger regional terminals. Compared to other vessel types in the short sea shipping sector, feeders operate more predictable routes, matching the mainline traffic between the hubs they serve.
For feeder vessels, optimising OPEX is the key to profitable and competitive operations.
Vessel type: Feeder container vessels
Typical size range: 500–3,000 TEU
Most optimal solutions:
General cargo vessels and short sea bulker vessels must meet a wide range of operational requirements. They can be chartered on short-term agreements, with highly variable voyage distances, loading conditions and sailing speeds.
Optimising vessel CAPEX and OPEX are crucial to securing the profitability and competitiveness for general cargo vessels and coastal bulkers.
Vessel type: General cargo vessels
Typical size range: 3,000–30,000 dwt
Vessel type: Coastal bulker
Typical size range: 3,000–30,000 dwt
Most optimal solutions:
When you seek reliability, high manoeuvrability and low or even zero-emission operations for your small merchant vessel, choose a partner such as Wärtsilä to deliver integrated solutions tailored to your needs.
Because the maritime transition toward sustainability is accelerating, the short sea shipping segment is facing a landscape of tightening regulations and shifting market expectations.
In the European Union: EU Emissions Trading System (EU ETS) and FuelEU Maritime are redefining compliance.
Globally: Benchmarks like EEXI and CII mean that even relatively young vessels must be evaluated to ensure continued operational eligibility and competitiveness. IMO’s Net-Zero Framework lays a solid foundation for marine decarbonisation towards and 2050.
In the market context: There is growing pressure from cargo owners, financiers, and charterers, who increasingly favour vessels with strong environmental credentials.
Newbuilds designed with integrated decarbonisation technologies, flexible power train, and digital capabilities are best positioned to meet both regulatory and client demands.
Existing vessels can consider strategic retrofits such as hybridisation, engine upgrades, and compliance-driven modifications.
Lifecycle planning will help owners make informed decisions on investments.
Wärtsilä’s smart propulsion system takes an integrated approach, combining engines, energy storage, propellers, electrical systems, and digital controls into a single, optimised solution. This ensures that the components work optimally together and deliver maximum efficiency, flexibility, and compliance from day one.
This propulsion system is modular and built around a medium-speed engine, controllable-pitch propeller (CPP), power take-off/power take-in (PTO/PTI), energy storage system (ESS), and energy management system (EMS). It can be tailored to your vessel’s operational profile, whether you need silent port operations, fuel savings on variable-speed voyages, or extra power for manoeuvering.
Key benefits:
This system is ideal for coastal tankers, feeders, and bulkers operating in EU-regulated waters or under charter conditions that demand both performance and adaptability.
The propulsion equipment consists of
Equipped with Wärtsilä’s smart propulsion system, your small merchant vessel can enjoy a long service life, meeting the current and future Carbon Intensity Indicator (CII) targets.
The Wärtsilä smart propulsion system is powered by a 4-stroke medium-speed engine offering unmatched fuel flexibility. The engine can be installed on resilient mountings to reduce vibrations and underwater radiated noise. Depending on the selected fuel type, Wärtsilä can supply an optimised combination of exhaust aftertreatment (SCR/Scrubber) and a fuel storage and supply solution
Power conversion onboard is based on an AC configuration with a DC hub. Power is supplied primarily by a variable-speed shaft generator during sailing and by shore connection in port. An auxiliary genset is provided as a backup. The shaft generator can also be used as a motor in PTI/PTH mode.
A battery-based ESS is connected to the DC hub to enable the hybrid functionalities of the Wärtsilä smart propulsion system. The energy capacity and power of the marine-certified lithium-Ion batteries are based on the vessel’s operating profile. The DC hub enables easy integration of additional energy sources like solar panels or fuel cells during the lifecycle of the vessel.
Fuel storage and supply can be adapted to multiple fuels, ranging from conventional liquid fuels and LNG to future fuels such as ammonia or methanol.
The integrated Wärtsilä Smart Propulsion System supports multiple operating modes to match the real-world demands of short sea fleets. Whether your vessel is manoeuvering in port, cruising under partial load, or idling at berth, each mode is designed to optimise fuel use, reduce emissions, and enhance reliability.
The main engine drives the propeller and the auxiliary genset provides the required electric power for the hotel load.
In mechanical mode, the vessel sails as a conventional vessel. This is the system fallback operational mode for any vessel operation.
The main engine provides the required power to the propeller and drives the PTO to supply the electric power for hotel load. The flexibility of the CPP is enhanced by the ESS, which ensures peak shaving, immediate load taking, optimised engine load and backup power.
This system operational mode is the most typical in sailing operation. It can be also used in manoeuvring operation.
The auxiliary genset provides the electric power for the PTI, replicating a small-scale electric propulsion system. The ESS is working in peak shaving mode.
Electric operational mode perfectly fits both in navigation at slow speed and in manoeuvring vessel operation, when the combination of a small-size prime mover and a supporting ESS ensures a substantial reduction in fuel consumption and emissions. Moreover, this operational mode provides a redundant “take-me-home” device.
The hotel and propulsion power are provided solely by the ESS.
As the batteries are providing the full electric load, this system operational mode can be carried out during relatively short periods of time both in navigation at slow speed or in manoeuvring modes, or may even become impracticable in case of high electric power demand depending on the cargo.
In this system operational mode the vessel can manoeuvre and navigate at slow speed in environmentally friendly mode with zero emissions and with minimal noise and vibrations.
The main engine and PTI provides the required power to the propeller. The auxiliary genset, in combination with the ESS, gives the power needed for hotel load and PTI.
This system operational mode allows the vessel to reach its maximum design speed, which typically has to be achieved only occasionally under exceptional conditions, while keeping the installed mechanical power to a minimum.
The main engine provides the required power to the propeller and drives the PTO which provides the required electric power for the hotel load and the manoeuvring thruster in combination with the ESS for peak shaving, backup power and immediate power.
For manoeuvring operation mode, the gate rudder plays a decisive role, allowing a smaller turning circle, a crabbing function and faster stops.
While shore connection is the preferential power source in port, the vessel can also operate independently when at anchor or in ports where the shore connection is not available. In this system operating mode, the auxiliary genset provides the electrical power for the hotel load, including ESS charging if needed.
The auxiliary genset can be sized according to the average hotel load, since the ESS absorbs the power fluctuations, e.g. from cranes or pumps during loading/unloading. As a result, the auxiliary genset runs at an optimized load, reducing fuel consumption.
In this back up mode, the engine is declutched from the propeller and is used in combination with the PTO as a genset to cover the hotel load and to charge the battery if needed.
This operating mode provides further redundancy in case both the shore connection and the auxiliary genset are not available.
The analysis with the technical and functional specifications of the propulsion machinery system helps the owner understand the full potential of the solution.
For the naval architect and ship designer, the analysis helps integrate the propulsion machinery system successfully into the vessel design.
Find a collection of helpful resources: Essential solutions for naval architects and ship designers
Certain retrofits can still benefit small merchant vessels that have some lifetime left. For example:
See how other small merchant vessels have benefited from solutions provided by Wärtsilä.
Choosing Wärtsilä means choosing a partner who understands the complexity of short sea operations. Wärtsilä can also delivers power, propulsion, and control solutions that work together in an optimal way.
Whether you're designing a new container feeder, coastal bulker or tanker, or general cargo vessel, Wärtsilä’s integrated approach helps meet emissions targets and reduce fuel costs. You can stay competitive in this changing market.
Take the first simple step toward a smarter vessel: talk to us about your project.
Parts of this page have been written with the help of AI. A human expert has checked all contents for accuracy.
