Ever since there have been outboard engines, inboards, stern drives, and jet boats, boaters have been arguing about which is best — and now, pod drives are part of this same discussion. But recent technological advances have vigorously shuffled the deck, and this topic is worth looking at with a fresh set of eyes.
Powerboats can run on several types of engines or engine packages, and in addition to those we’ve already mentioned you may also need to choose between single and twin engines, or between gasoline or diesel. Even electric or hybrid power may be in the running. Different options work better with different types of boats, and limited choices are offered with most boat models. Naval architects and engineers use complex formulas to determine the correct range of engine options for a given boat, and then you get to choose. So naturally, the type and size boat you’re considering will, to some degree, dictate the engine choices you’re presented with. That means you don’t need calculus or a super-computer to make good boat-buying decisions, and your job is merely picking the best power options from those offered for a given boat that meet your needs.
Boat Engine Advantages
Different types of boat engine and propulsion systems have unique plusses and minuses, so let’s look at each in detail.
Modern outboards have a long list of advantages. Start with their newfound reliability; while you could count on those old-tech outboards to break down with depressing regularity, these days, it’s common to go for five or six seasons without lifting a finger beyond regular maintenance. Then consider their comfort factor. Today’s outboards are smoke-free, quiet, and don’t create nearly as much vibration as those of yesteryear. They also tend to have excellent efficiency, even while attaining speeds in excess of other power systems. And a new option with outboards is joystick control, which greatly enhances dockside maneuverability. Finally, if an outboard engine needs replacement it’s a far simpler job than replacing any other type of power source.
We do want to note that when choosing outboards, you’ll further have to choose between two-stroke and four-stroke models. Both types of outboards have undergone major changes in the past decade, so before making any decisions, be sure to watch our video on Two-Stroke Outboards Versus Four-Stroke Outboards.
Inboards and V-drives
Inboards are the most traditional form of power for a boat, and although there have certainly been technological advancements made with this type of powerplant, they’ve probably changed the least over time when compared to the others. One often-overlooked advantage they have over some power systems is weight distribution. All other things being equal, placing the weight deep in a boat’s belly often enhances the ride and increases its stability. On top of that, the sky’s the limit when it comes to horsepower range with inboards. Plus, you also get to choose between gasoline or diesel (more on that later).
When it comes to inboards you also have the option between straight-shafts, and V-drives. A V-drive allows the engine to be placed facing forward, but in the very rear of the boat. The forward-facing shaft mates with an aft-facing one which goes down through the bottom of the boat, forming a “V” shape. Using a V-drive allows boat designers to create more interior space than you’d find in a conventional inboard boat, which has the motor located significantly farther forward.
Pod drives have all the advantages of inboards, plus a few more. The articulating drive systems make handling second to none—with a pod drive joystick at your fingertips, it’s easier to dock your boat than it is with any other power system. Efficiency goes up as compared to inboards (remember that pod drives provide angle-free thrust), sometimes by as much as 25 percent. And the elimination of shafts and the required shaft angle allows designers to gain cabin space, since less room is needed for the engine compartment.
Stern drive power systems, like outboards, have gotten a handling boost from joystick integration. And, of course, they give you the ability to change your draft and adjust running angle via trim when necessary. While they don’t provide as big a weight distribution advantage as inboards, they do have a leg up in this regard compared to outboards. And do-it-yourselfers often favor stern drives for the easy engine access, and automotive-like familiarity of the powerplant.
The jet drive advantage is obvious: with no propeller spinning beneath the boat, you never have to worry about the propeller getting damaged—or doing damage. Truth be told prop injuries are extremely rare, but it’s still a possibility that many people want to eliminate entirely. That makes jet drives a favorite of many new boaters, particularly those buying small family runabouts.
Power System Disadvantages
What about the down-side to each form of boat propulsion? Again, let’s pick each type apart in detail.
They may have come a long way, but as they’ve progressed, prices have gone up accordingly. A modern 250-hp powerplant will cost you upwards of $20,000. And today’s outboards are extremely technologically-advanced — forget about doing much more than an oil change without a visit to the dealership. While outboard joysticks are an awesome new development, generally speaking, you can’t expect them to handle quite as well as pod drives. Your power choices are limited in size, as well, since mass-produced outboards top out at 425 horses (though there are some larger options such as Seven Marine’s limited-production 527, 577, and 627 horsepower models made from a marinized 6.2L Cadillac engine; see Seven Marine Expends and Refines its Outboard Line, to get the full scoop). And with very few exceptions, diesel is not an outboard option.
Inboards and V-Drives
These are the only power systems on the water today with drives that don’t articulate; they still depend on rudders for steering. As a result, their handling (except dockside, when opposing a pair of twins allows you to effectively spin on a dime) isn’t as good as it is with the other options. The same is true of draft. Other than sailboats, no boats require more water under the keel than straight inboards. Inboard-powered boats also suffer from more drag than the others, thanks to their running gear, which translates into less speed and efficiency. And an inboard eats up a lot of space inside the boat.
This power choice is an expensive option, although they’re usually found on larger boats where the percentage of overall cost isn’t out of line. Many people are scared off from pods simply by the idea of having those large holes in the hull for the drive units. Getting the drives serviced can also be expensive and time-consuming, depending on where you’re located. Finally, remember that a boat has to be designed specifically for pods — you can’t repower with them, and when existing boat models are modified to carry pods the builder may encounter additional design costs. You can expect that these costs will be passed on to you, the consumer.
Stern drives are known for having maintenance issues. The boot and outdrive systems, in particular, tend to require a lot more attention than simpler drive units. And in some cases a lack of maintenance (particularly with the boot) doesn’t cause a mere trifling breakdown — it can flood the boat. Stern drives also eat into cockpit space in some boats (especially on smaller models) because they may require a raised motor box. Many single-screw stern drives also wander quite a bit at slow speeds, and require constant steering corrections.
Jet boats have a number of drawbacks weighing against their big prop-free advantages. There’s a significant loss transferring power into thrust, which makes jets less efficient and slower in the mid-range. This also means that in many cases, jet-driven boats struggle to get onto plane unless the throttle is buried. They also tend to be very loud and high-pitched. And handling at slow speeds, which can range from great to atrocious, requires some getting used to.
Diesel, Gasoline, or Electric?
For the most part, you won’t have to make a gas-versus-diesel decision unless you’re buying an outboard or an inboard. The few stern drive diesel options share the same benefits and deficits as with inboards, jets are virtually all gas-powered (with some commercial application exceptions), and pod drives are all diesels (again, with some commercial exceptions).
Depending on which of these power systems you’re choosing from, you may also be presented with options between gasoline, diesel, electric, and even propane as well. However, although outboards are available in all of these forms, the vast majority are gasoline-powered. A handful of diesel options are out there (Mercury Racing has dabbled in diesel with an OptiMax model, BRP has done the same with an MFE multifuel option, and there are a handful of others) but the field is extremely limited. The choices for electric outboards are wider-ranging, particularly in the low horsepower market, with most of the higher-powered options coming from Torqeedo Electric Outboards. These top out at 80 horsepower with the Torqeedo Deep Blue, although there are also a few small manufacturers attempting to market more powerful versions.
Propane is limited to small models as well, with Lehr dominating the market and offering engines up to 25 horsepower. Recently, Tohatsu introduced a five horsepower propane model as well.
We run down the advantages and disadvantages of each of the options other than gasoline, in detail, in Alternative Power: Outboards That Are Gasoline Free.
Inboards and Stern Drives
Diesel is much more common when it comes to inboards, particularly in large boats. In fact, once you start looking at boats over 35 or so feet in length which have inboards or pod drives, gasoline engines simply don’t have the horsepower and torque to get the job done. As a result, most motor yachts, convertible boats, trawlers, and similar vessels are usually powered by diesels. Diesels offer outstanding durability under frequent use, far better than that of gas motors. Plus, they also have a much longer working lifespan. On the other hand, they do cost substantially more than gas engines. If you plan to use your boat often, spending the extra money on diesel power – if it’s available – might be wise. This is especially true if you buy a heavy boat that demands lots of muscle to push it through the water.
For an in-depth look at gasoline versus diesel, take a look at Boat Engines: Choosing Gas or Diesel.
In a few rare cases, hybrid electric power is offered on inboard boats. These are usually systems that are specific to a builder or even a single model in a builder’s line. The Greenline 40 is one popular example, and Beneteau also offers a hybrid model, the Hybrid Swift Trawler 34.
For a run-down of the hybrid electric options out there, see Hybrid Electric Power: Will Your Next Boat Have It?
Which kind of engine do you need for your boat? By now, you should realize that it depends on the type of boat you want and the type of boating you enjoy. But we can say one thing for sure: whether you opt for outboards, inboards, pod drives, stern drives, or jets, todays boat engines are more reliable and easier to run than ever before.
Editor's Note: This article was originally published in July 2014 and updated in September 2018.