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Marine Power

How to Buy Power

Wondering which propulsion package to pick for your next boat?
Here are some things to consider.

My father was a great believer in the power of cold, dispassionate logic to  arrive at the best solution to a problem, and he spent much of my childhood imparting this belief to me. Time and time again I watched as his vaunted “decision tree” took him unerringly to the right answer. But in 1960 he taught me another lesson when he brought home a brand-new Pontiac Bonneville convertible, the least-logical car he’d ever owned. The lesson was obvious: Sometimes it’s OK to let your heart outvote your brain.

One of those times is when buying a boat, a process that defies logic. Only a commercial fisherman needs a boat, and the bloody things are unrelentingly demanding of time and money. But who cares? 

Still, this doesn’t mean logic shouldn’t play some part in your boat-buying process, and if it has any place in it, surely it is when you grapple with the issue of propulsion. The propulsion system will represent the single largest expense in your next boat, and if that renders you sufficiently sober to at least ponder a few considerations, then read on.

To prevent the logical consideration of a propulsion system from turning into a major buzzkill, I’m going to prune this decision tree down to just two large limbs: performance and resale value. This is not to say that other considerations, such as a manufacturer’s reputation, the availability and quality of service, and your own personal experiences are unimportant. They are, and in some cases they may even be the deciding factor. But even then you’ll want to at least ponder the value of these two factors.

First, the good news: There are no bad marine diesel engines currently on the market, at least that I know of. It’s true that every manufacturer has at one time suffered from a defect that has required a recall or some other fix but as a general rule, in terms of reliability, longevity, and efficiency, the qualitative differences among the various brands are too small to sweat. Admittedly, in specific applications, one particular engine model may be superior to all others, but in terms of general engine quality, the major brands all have a pretty good record.

Now the bad news: While the quality of modern marine diesels is uniformly good, the same may not be said of service, and since all engines need service at one time or another, you need to factor that into your decision. If you have had a good experience with a particular distributor for instance, staying with that outfit, and by extension that engine brand, is a worthy idea. So is asking fellow boaters about their experiences. By the same token, if you’ve come to trust a particular mechanic, you should solicit his opinion as part of your research.

But when it comes down to actually checking the box on the order form indicating which propulsion system a boater is going to shell out his or her hard-earned dollars for, the most common question is typically, How fast will these engines make my boat go? Nearly all boatbuilders will readily supply you with test results providing the answer, and my experience in testing all kinds of boats tells me these results, while they may tip toward the optimistic side, nevertheless are accurate enough to provide you with a valid yardstick. But in looking at them make sure you focus on data that will be meaningful to you. 

It’s probably futile for me to tell you to ignore top speed—but if you can, do. No one in their right mind spends any significant time running at WOT—which my mechanic says really stands for With Out Thinking. Cruising speeds are what you want to focus on, and when you do you may discover that the difference between various powerplants at particular cruising speeds is a lot less than it is at full throttle. Indeed, backed off to a modest cruising speed, a less powerful package may often equal the speed of the top choice—which means in terms of knots per dollar, you’re getting zero return on your extra investment. But as we’ll see, there’s more to consider regarding return on investment.

If you’re obsessed with speed, keep this in mind: The relationship between speed and horsepower is geometric; the faster a boat goes the more horsepower is needed for a given increase. So if you need to go 30 knots instead of 25, it’s going to take a lot more horses—and money.

The other issue to consider was once nicely articulated to me by Jack Leek of Ocean Yachts: “It’s not what you pay for a boat, it’s what you sell it for.” Most of us don’t keep one boat for our whole lives, which is why we ought to consider what we’ll get for it when we trade up—or sell out altogether. In some cases—say, a sportfisherman—boats with the most powerful engines will command significantly more at trade in, and their ability to return more of their initial investment is a factor that can dwarf all other financial considerations. In other boats, especially long-range cruisers, a more powerful engine package may have less value. To find out which category your particular boat falls into requires research, starting with a reliable broker and a perusal of used-boat listings.

But enough of logic. It’s boat-show season, the best time to give free rein to your emotions. So be logical, but above all, enjoy the process.

This article originally appeared in the January 2016 issue of Power & Motoryacht magazine.