Engines on Catamarans: Outboard vs. Diesel – Which is Right for You?
One of the biggest differences between catamarans and monohulls is their twin-engine setup, providing better control, redundancy, and fuel efficiency. But not all catamarans are powered the same way—some rely on outboard motors, while larger, heavier catamarans use diesel inboards. Each has its own advantages and trade-offs, depending on the type of sailing you plan to do.
In this guide, we break down the key differences between outboard and diesel engines on catamarans, helping you understand which is best suited for your needs.
The Twin-Engine Advantage of Catamarans
One of the major benefits of catamarans is that they typically come with two engines, providing:
Redundancy – If one engine fails, you can still use the other to get home.
Better Manoeuvrability – With engines spaced apart in each hull, you can pivot the boat in place for easier docking.
More Efficient Handling in Waves – Twin engines give you greater control when dealing with strong currents and wind.
Outboard Engines on Catamarans
Many smaller and lighter catamarans (often up to 15 metres) are powered by outboard motors, which offer some unique benefits.
Advantages of Outboard Motors:
Lower cost – outboards are significantly cheaper to buy, install, and maintain compared to diesel inboards.
Ease of maintenance – they can be serviced or replaced easily, and parts are widely available.
Shallow draft flexibility – many outboard-powered catamarans allow you to tilt the engine up, reducing draft and making it easier to anchor in shallow waters.
Disadvantages of Outboard Motors:
Ventilation issues – in rough conditions, the propeller may lift out of the water, causing ventilation and loss of thrust.
Fuel type – most outboards run on petrol, which is more flammable than diesel, raising safety concerns.
Exposure to elements – since outboards sit on the stern, they are more exposed to saltwater and weather, leading to faster wear and tear.
Limited power for onboard systems – outboards are only used for propulsion; they don’t generate power for onboard systems like fridges, watermakers, or large battery banks.
Best for:
Outboard engines are ideal for lighter, performance-oriented cruising catamarans, especially if you prioritise cost savings, simplicity, and shallow-water anchoring.
Diesel Engines on Catamarans
As catamarans get larger and heavier, they typically transition to diesel inboard engines, offering better power and fuel efficiency.
Advantages of Diesel Engines:
More torque and power – diesel engines swing larger propellers and provide better thrust in rough seas, making them more reliable for long-distance cruising.
Lower fuel consumption – diesel is more efficient than petrol, meaning longer range and lower operating costs over time.
Less flammable – diesel fuel is safer to store on board compared to petrol, reducing fire risks.
Powers onboard systems – diesel engines can run alternators, watermakers, and refrigeration, making them essential for off-grid cruising.
Disadvantages of Diesel Engines:
Higher initial cost – diesel engines are more expensive to buy and install than outboards.
Permanent propeller immersion – unlike outboards that can be lifted, diesel inboard propellers are always submerged, leading to corrosion risks and requiring anti-fouling protection.
Increased draft – since diesel engines are fixed in place, they limit how shallow the boat can go, making certain anchorages less accessible.
More complex maintenance – while durable, diesel engines require more maintenance and professional servicing compared to outboards.
Best for:
Diesel engines are the preferred choice for heavier cruising catamarans, bluewater passage-making, and boats that need reliable power for onboard systems.
Which Engine Type Is Best for Your Catamaran?
Choose Outboard Engines If:
You want a more affordable, easy-to-maintain system.
You plan to sail in shallow waters and need a tilting propeller.
You’re sailing a lighter performance catamaran and don’t need onboard power generation.
Choose Diesel Engines If:
You need more power and fuel efficiency for long-distance cruising.
You want to run onboard systems like fridges, watermakers, and battery chargers.
You sail in open ocean conditions where strong headwinds and rough seas require extra thrust.
Final Thoughts: Choosing the Right Engine for Your Catamaran
Both outboard and diesel engines have their pros and cons, and the right choice depends on your sailing style, budget, and needs. If you value simplicity, cost-effectiveness, and shallow-water access, an outboard-powered catamaran might be perfect. But if you're planning offshore cruising and need reliable power for long distances, diesel inboards will provide the performance and efficiency you need.
Want to learn more about handling and maintaining catamaran engines? Join one of our hands-on sailing courses, where we cover everything from basic engine maintenance to troubleshooting at sea.
