Boat Motors: Outboards, Inboards, Pod Drives, Stern Drives, and Jets
Modern technology has changed inboards, outboards, stern drives, and jets, and added pod drives to the list. But, what sort of boat engine is right for you?
Ever since there have been powerboats boaters have been arguing about which is power system is best, be it the latest outboard engines, old-school inboards, stern drives, jet boats, or pod drives. 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. These days we also have to add electric motors to the list, which most commonly will be in the form of electric outboards. And those interested in pontoon boats may also have the option of a Rotax S, which is like an outboard but it mounted on a horizontal plane underneath the swim platform.
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 engines and propulsion systems have unique plusses and minuses, so let’s look at each in detail.
Outboard Motors
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. Since the engine is outside of the boat's cockpit, interior space is maximized. They also tend to have excellent efficiency, even while attaining speeds in excess of other power systems. And a great option often offered 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.
Electric Outboards
Electric outboards have gone from obscure to grabbing headlines in recent years. Their advantages are obvious: they don't burn any fuel. That reduces operational expenses (though there's more to consider on the full cost picture, which we'll dive into later). Another big plus of using these motors is that they're virtually silent, and many boaters report having a more pleasant experience running them. In addition, they're incredibly reliable.
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 since there are plenty of very large diesel inboards in production today. Plus, you also get that choice between gasoline or diesel.
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
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 drives
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 sometimes favor stern drives for the easy engine access and automotive-like familiarity of the powerplant.
Jet Drives
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.
Rotax S
A new and unique option on the water is the Rotax S. This is a one-of-a-kind system in which the powerhead sits horizontal in a watertight cowl, greatly reducing its height. This allows for it to be mounted underneath the swim platform, boosting the platform's useable space and reducing sound levels. BRP also claims an efficiency gain. Currently, the Rotax S is available on Manitou pontoon boats.
Power System Disadvantages
What about the downside to each form of boat propulsion? Again, let’s pick each type apart in detail.
Outboards
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 $25,000. 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 600 horsepower. And while choosing diesel is an option, the choices out there are very limited.
Electric Outboards
The biggest problem with electric outboards is the amount of battery power needed to feed them, which means electric rigs generally have a very limited range as compared to gasoline. When operated at planing speeds, boats that might have a range of hundreds of miles might see that drop to 20 or 30 miles. And, while the motors themselves aren't outrageously expensive, those new LiFePO4 batteries certainly are. In fact, they can push pricing to triple or even more than that of comparable gasoline-powered outboard rigs.
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. They also require much more draft than options aside from pod drives. 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.
Pod Drives
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. Some 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
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 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 Drives
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. Some 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.
Additional Options for Boat Motors
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?
On top of all these systems there are a few options for propane-powered outboards, though most are very small and there are only a handful of choices on the market. There are also some natural gas solutions, which are conversion kits made to work with outboards originally designed for gasoline. And in 2024 a new option was floated, when Yamaha announced the first-ever hydrogen-powered outboard motor. Boats need to be purpose-built for hydrogen systems due to the special tanks that are required, and as of now this is in the early prototype stages, but it certainly shows some serious innovation in the industry.
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, today's boat engines are more reliable and easier to run than ever before.
Editor's Note: This article was originally published in July 2014, updated in September 2018 and March 2020, and most lately in June of 2024.
