Outboard engines come in an array of configurations. When you buy a car, it tends to come with an engine, leaving you very little to think about other than the colour of the paintwork and the best place to hang your fluffy dice. But in the marine world, we have the luxury of choice - not just between manufacturers but also between weights, outputs and even methods of power generation. And that’s to say nothing of the retro-fit market, where an engine can be fitted to a bare boat or used as an upgrade for an existing unit.
In the past, picking an outboard engine tended to be a fairly simple choice between two and four-stroke. On the one hand you had the lightweight simplicity of two-strokes, with their excellent hole-shot and vigorous throttle response - and on the other, you had the promise of cleaner, smoother, more refined operation. But the need to comply with environmental standards (and the modern customer’s wish to pick the cleanest and most efficient option) has seen the choice of outboards expand enormously, with four-strokes now available from two to 350hp, plus Direct Injection two-strokes across a slightly less extreme power spectrum and an ever-expanding range of squeaky-clean electric options.
How to choose right outboard engine: 10 tips
- Consider the engine weight as well as its output.
- Think about security, as thefts of outboards are all too common.
- Take advice from the boat builder about the best options for your craft.
- If possible, test drive a couple of different engine options on the same boat.
- If you can’t afford a new engine, think about reworking/upgrading your prop (see How to change a propeller).
- If you like watersports, Evinrude’s clean, torque-generous G2s should be on your list.
- If you do most of your boating inland, consider Torqeedo’s electric options (see Torqeedo electric outboards).
- Think about the ‘peripherals’ (data displays, security features and service back-up).
- Price is obviously important but also consider the likely long-term running costs.
- Don’t discount the used market, as there are some very big savings to be made.
Direct Injection two-strokes
The latest Direct Injection (DI) two-stroke outboards employ sophisticated engine management systems to produce a combination of performance, economy and refinement radically removed from their simplistic two-stroke predecessors - and most of this is achieved by improving the method by which fuel is introduced into the cylinders.
The most recent models (primarily from Evinrude, Mercury and Tohatsu) shoot a very precise amount of fuel into the combustion chamber at exactly the right time. This replaces the more approximate methodology of the carburettor and not only does it mean that the fuel is better atomised, but it also results in a cleaner, more complete burn, with no fuel wafting into the chamber and inadvertently spilling from the exhaust port.
As regards lubrication, a precisely metered stream of oil lubricates the rings and bearings before ﬂashing off in the combustion chamber. This oil then exits along with the exhaust gas, but the proportion of oil burned is tiny and its impact on emissions is minimal. In short then, a modern DI two-stroke offers plenty of the traditional low-end poke we all love, while bringing cleanliness into line not just with modern environmental sensibilities but also with challenging modern fuel prices.
However, the most striking progress with DI two-strokes in recent times has come from Evinrude, with the introduction of its G2 engines. Not only can they be exactly colour-coded to match your boat, but they come with the steering cylinder integrated into the swivel bracket alongside the power steering unit, which means easy rigging and no messy cabling in your engine well. They also come with an automated Trim Assist function, plus adjustable steering settings and a very user-friendly, 500rpm, low-emissions setting at idle. Of course, the prices of the G2 engines now exceed most four-stroke offerings by around 10 per cent but then the Evinrude G2 is not just an outboard; it’s a fully integrated and readily customisable propulsive solution.
Big strides for four-strokes
For a lot of leisure boaters, four-stroke outboards remain the number one choice - and The biggest players in the modern marketplace are Yamaha, Suzuki, Mercury and Honda. Most use a fuel-injection system developed from the sophisticated multi-port technology of the motor industry, with one injector per cylinder generating crisp throttle response and vast improvements in economy. However, as four-strokes only produce power on every other up-and-down movement of the crank, they have tended in the past to lose out to two-strokes on low-end performance. To compensate for that, many manufacturers now incorporate a lower gear ratio, thereby increasing torque and closing the gap in ‘hole-shot’ performance.
On the water, this means that those of us who lamented the end of the traditional two-stroke can cheer up, because with the modern four-stroke, you get most of the performance benefits, alongside ever improving levels of refinement. The continual reduction in physical size and weight also means a broader range of power outputs are being brought into the frame for the transoms of more compact boats - and at the other end of the scale, some truly epic 350hp and even 400hp engines from the mainstream manufacturers mean that far larger boats can now embrace the benefits of outboard power.
What about the small stuff?
For small boats, there are certainly lots of old outboards on the used market, with prices from as little as £100 for a 2hp Yamaha or Suzuki. But if you want a shiny new internal combustion outboard at this level, your only option is four-stroke - and they are astonishingly frugal. A two or three horsepower unit on a well-matched runabout could easily provide a full day’s entertainment for a fiver. Of course, it’s more expensive to buy (from around £500 to £600 for a new 2.3hp four-stroke) but other than a lower purchase price and a simpler maintenance programme, the older style two-strokes now offer no practical benefits over these modern engines.
So what about an even newer technology - namely electric outboards? They are well suited to small boats and inland applications, with easy portability, quiet propulsion and cheap running costs. The batteries are likely to need replacing every three years or so, but that is offset by the fact that you don’t need to buy any fuel. With prices from around £100 to more than £3,000 from names that include Flover, Mini Kota and the German specialist, Torqeedo, electric outboards go from simple trolling motors to remotely operated units that can power even sizeable boats. They are very compact and lightweight, and because a full overnight charge can be well under a pound, the running costs are fantastically affordable. In short, if you own a small boat, the modern breed of clean, reliable, low-maintenance electric outboards should not be overlooked. For more on these see Lenny Rudow's feature Solar power for boats.
Summary: the key to buying the right outboard
These are exciting times for outboard buyers, with rapidly developing technologies reducing weights and increasing efficiency, not just with internal combustion but also with electric propulsion. It is true that the price of a new outboard often exceeds the value of the boat to which it is fitted. However, if outright speed is not your sole mission, then there are a great many ways to give your boat a fresh lease of life with some affordable new power. For my top 10 engines, see 10 top outboard engines.