There’s a growing interest in power options, for motor yachts and auxiliary sailing yachts alike, that are more sophisticated than the simple, traditional shaft drive.
Fuel costs are a major factor driving this interest. While they’re unusually low at the moment, they won’t stay that way forever. And even if cost isn’t much of a concern for you, range under power probably is—getting a bit of extra distance out of the same tankage volume can make a big difference to your cruising plans.
Fuel consumption, though, is not the only factor that can spark an interest in more sophisticated powertrains. Perhaps you want:
- Lots of thrust at low speed for towing and for docking in tight quarters.
- Or the silent, odourless operation of an electric drive for poking around in quiet, unspoiled rivers.
- Or an engine that can provide an extra boost for motorsailing just as efficiently as it can drive the boat on its own.
- Or you just want to stop tearing apart your diesel to re-hone its badly glazed cylinder walls every time the thing acts funny. (Many yacht engines die from being used at low loads.)
Just as often, I see people choosing fancy, high-tech equipment simply for the sake of having the latest, coolest toys to play with and to show off. Honestly, I’m OK with that. It keeps plenty of my friends in business.
Fooling youself about your motivations, though, can be dangerous. If you want a $90,000 hybrid electric drivetrain for the sake of having the coolest engine room at the boat show, that’s fine, but if your intent is to save fuel, money and repair time then I may very well recommend you look at something else instead.
A Closer Look
In this series, we’ll explore the advantages and downsides of various “advanced” drivetrain technologies, and take a look at the logic by which we might select or reject them for our boats.
Some of these technologies—hybrid electric drive in particular— are awash in marketing hype, much of it unjustified or exaggerated. We’re going to try to cut through all that, focusing instead on the questions that really should guide the decision:
- Does this system make sense, from a technical standpoint, for my boat?
- Does this system make sense, from a cost standpoint, for my boat?
- Can I live with this system in remote areas and over many years?
Each of us is in a different situation, so we can’t draw any specific conclusions along the lines of “You should buy System X”. We can, however, get a pretty good idea of what each technology’s strengths and weaknesses are, how these systems are likely to perform in real-world cruising, and how to go about deciding what makes sense for you.
We need to start this discussion from solid, well-understood ground. To that end, the next two chapters of this Online Book are about shining light on things we like to think we’re pretty familiar with:
- Diesel engines, how their efficiency varies over the operating range (RPM), and why boat engines are often used in a non-ideal way.
- Propellers, the factors driving their efficiency (or, more commonly, their horrifying lack thereof) and what we can do to improve it.
Then comes the fun stuff. We’ll look at:
- controllable-pitch propellers;
- multi-speed and continuously variable transmissions;
- and the wide range of electric and hybrid-electric systems
to see what, if any, of this technology is appropriate for our cruising yachts, both power and sail.