There are always trade-offs



The economist Milton Friedman was fond of using the cliche, “There’s no such thing as a free lunch” when discussing economics. When deciding on powering a vessel or industrial application, there are always trade-offs involved. There really is no such thing as a free lunch.

When choosing how to power a vessel, pump, vehicle, or generator, the first step in providing the appropriate power source is listing what the important functions should be:

  • Is weight critical?
  • Is reliability most important?
  • Is fuel economy most important?
  • Is reliability most important?
  • Is the availability of parts and service most important?
  • Is torque most important?

The questions go on and on.


Just like Friedman’s free lunch is bound by economic law, power applications are bound by the laws of physics. They are unalterable.

If you are designing a boat that will be used as a tug boat, MarineDiesel’s VGT Series is not a good match, even if compared to a similar, say 500 hp engine. Why? The VGT Series is designed for high speed operation, and Bollard Pull is not one of the VGT’s benefits. The engine was not designed to operate under that load. Were you to use it in that application, your service life would decrease sharply due to overload. Likewise, a 12 litre engine would power a small tugboat adequately, but would be far too large and heavy to operate on a light, high speed craft. The trade-off? Pulling force is sacrificed for weight on the VGT.

To further illustrate, suppose the engine is being used to power a RHIB with a tiny engine compartment. What happens if you install an engine and all of the major components are inaccessible? Your service costs will certainly go up the first time a water pump needs servicing. The VGT was designed with ease of service in mind in small engine compartments. A few thousand EURO savings on purchase may not be such a good deal when you need to pay many thousands of Euro in cutting an engine out of a hull in order to replace that pump.

Performance is one of those terms that is thrown around rather carelessly in the engine business. Performance really is a single term that asks, “Does this engine do what I need it to do?” There is no right or wrong answer to this question. MarineDiesel designed our VGT engines to be very flexible in performance. That is why we use the programmable NIRA ECUs, for instance.

However, though we can program the engine electronics, there is always a trade-off between benefits. You can never have it all. Want more high-end torque? OK. We can do that. But your service schedule and life cycle will change, and your fuel consumption will increase. Want longer service life? We can do that, too. But your top speed will suffer.

It is all a question of trade-offs, rather than simply price.