Power and the Single Engine Strategy
Powering the NAVA 38 is a single, new generation, lightweight, high output, turbocharged, after-cooled “Yanmar” marine diesel engine of 440 hp. These modern diesel engines provide a fantastic power to weight ratio, reliability, low maintenance requirements, and inherent efficiency. They’re also cleaner running and quieter than earlier technology.
Modern diesel engines are sufficiently reliable that a second engine is not necessary for safety and maneuverability concerns are over come with thrusters.
The concept of just one engine with no sacrifice in speed, compliments the performance, simplicity and efficiency strategy of this yacht. If all the extra weight and inherent inefficiencies associated with a second engine are added up, one quickly realizes the majority of the additional power generated is not necessarily providing much further speed, but is just sustaining the weight of the second engine and all it’s associated equipment. The entire focus of the boat becomes more that of a "life support system" for two engines.
Consider the weight of the additional:
engine bed and mounts
heavier stringers and hull structure for support
propeller shaft and coupler
propeller shaft strut and bearing
fuel filters and plumbing
680 + liters of fuel or 180 US gal (1300 lbs. +)
sea water strainer and plumbing
controls and instruments
onboard spare parts
Not to mention:
Significant additional resistance of the second set of underwater appendages
Additional initial cost of equipment
Added ongoing operating and maintenance costs
Increased exhaust emissions
Diminished handling and performance
Other benefits are far more space in the engine room for mechanical systems and improved serviceability, and greater options for roomier living accommodations.
The bottom line is one engine makes for a simplified, more efficient, nimble craft.