The azimuth stern drive (ASD) ships will be delivered in 2015.
No price was given, but the vessels will be built in Vietnam and Romania.
Two are ASD 3212-types and will be sisters to an 83-bp unit built by Damen in 2012.
The other is a 61-bp ASD 2810 Hybrid.
The propulsion system uses diesel, electric and battery power, cutting fuel use by up to 30% and reducing emissions by 60%.
