One engine or two engines on a 20 tonne displacement boat ?

Question

Is the single engine more efficient ? Can one engine be used to drive two props. ? Will twin engines provide better manouverability ? The boat is to be used offshore and on inland waterways.

Answer 1

There are many variables to be considered. Yes a single is slightly more efficient but you do sacrifice a margin of safety (not likely both engines would fail at the same time) and close quarters handling. Thrusters can help overcome the handling issue. It comes down to what you can afford and personal preference. I prefer twin engines. There was an article in a trawler magazine about a boat that the owner pulled both engines out and replaced them with a single diesel generator that provided power for twin electric motors. It worked well for him and gave the economy of a single with the handling of twins.

Answer 2

Most twin engines fail because of fuel problems so it tends to affect both at the same time. Single engine has to work harder so it needs to be big to do the same work. Bow thrusters are imperative with single engine. Twin engines give

much more maneuverability even without thrusters.

Answer 3

one large diesel engine will do the job if speed us not a factor. you will need bow and stern thrusters for docking.

Answer 4

While there are many advantages to twin engines but you also need to consider that your initial cost will be far greater, space occupied, and ongoing mtce costs now x 2.

If you can get away with one engine and install a bow thruster then this would be a cheaper option. Mind you with one engine you loose your safety aspect in the case when an engine fails.

A lot to consider.  but if money is no object then twins is the go.

With Twin Engines - Having wing tanks (seperate fuel tanks) for each engine reduces any fuel issues affecting both engines.