Fossil fuels—and biofuels, for that matter—are offensive to both your nose and the environment, but other fuels simply don’t have the same punch as petrol... or do they? New forms of alternatively powered outboards have come onto the market in recent years, and they’re surprisingly promising. Let’s take a look at some of the options you now have to become a petroleum-free powerboater.
1. Zap and trickle: Electric outboards
Electric power is the most common alternative to petrol when it comes to outboards, but due to battery constraints – size and cost – the range for an electric engine is much more limited than that of a petrol engine.
One of the best-known manufacturers of modern electric outboards, Torqeedo, addressed this issue by not only producing electric motors, but also a line of sealed, waterproof (to IPX67 standards) lithium batteries designed specifically for their motors.
Lithium magnesium (LIMA), lithium nickel magnesium cobalt (LNMC), lithium ion (Li-ion), and other derivatives all belong to the family of lithium batteries, and compared to traditional batteries they’re lighter, hold their charge better, can handle more charge/discharge cycles, and don’t have charge-memory problems. Unfortunately, some can also be quite volatile, even causing open flames on rare occasions.
This volatility is part of why Torqeedo designed its own battery, and why they include computer-controlled charging and monitoring systems with multiple redundant safety functions. Smaller motor models in their line, like the Ultralight 403 and the Travel 503/1003, provide up to four horsepower and feature integrated batteries potent enough to provide range up to 20 miles. True, this range comes only at slow speeds—the Travel 1003 will push a small boat at 2 knots for over 10 hours, yet can only maintain a top-end of 5 knots for about 35 minutes—but the integrated battery weighs less than 4.5kg (10lb), which makes carrying multiple back-up batteries an option.
This, however, also brings us to another down-side of electric propulsion: it can be expensive. Very expensive. Back-up batteries cost over £350, and the least expensive Torqeedo, a 1.5hp Travel 503, starts at about £1,200.
2. Maximum Torque: Torqeedo Deep Blue
The Torqeedo line also includes 5, 8, 40, and the recently introduced 80hp Deep Blue.
Naturally, larger motors require a bit more punch than the integrated power cells used on the small models. Again, Torqeedo designed and built a battery specifically for heavier marine use: the Power 26-104. This LNMC power-pack zaps out 2,685 watt-hours yet weighs in at 25kg (55lb), which means pound-for-pound it has over twice as much punch as most conventional batteries.
We tested a pair of the 8hp (Cruise 4.0 RL) Torqeedos with four of these batteries on a 4.2m (17ft) flats boat at the Miami Boat Show, and we hit 14.7 knots. Torqeedo says the boat can maintain that speed for over an hour.
Excluding the boat, this 16hp rig would cost nearly £12,500. And while the £15,000 cost of a single 80hp Deep Blue alone seems fairly reasonable, with the four larger, more powerful batteries Torqeedo recommends, plus chargers, and controls, the complete system pushes £60K. Ouch.
When considering cost, of course, electricity-lovers always bring up the fuel-savings but, even if you ignore the price of the electricity for charging the batteries, you’d have to chug down over 37,000 litres of fuel before seeing any savings. Again, we say ouch.
3. Alternatives to Torqeedo
ReGen Nautic, has a 180 HP model that was recently tested on an 5.5m (18ft), 907kg (2,000lb) Campion Chase 550 bowrider. The boat hit a top-end of 43.5 knots (50mph), and at 39 knots, the package hummed along for two hours. And there's a 300hp model on the way.
Published cost for the 180hp model (engine only) is £15,200 ($25,587), and for the 300 HP model is expected to be £25,600 ($43,187).
4. Fish fry: Trolling motors
Electric trolling motors range from diminutive models that cost under £100, put out about a third of a horsepower and offer hours of operating time on a 12-volt deep cycle battery, to larger, more expensive models that overlap somewhat with the low-powered end of Torqueedo’s range, producing a couple of horsepower and costing several thousand pounds. There are also more complex, feature-ridden models that can do things like interface with autopilots, GPS, and fishfinders, operate via foot-controls, and even follow depth contours automatically.
Their use is wide-spread in the USA (less so in UK), their reliability is proven, their utility is great, and their cost is low. If you were powering a small boat in a pond or lake, for example, you could get a basic motor-and-battery rig that puts out about one horsepower and could drive the boat at three or four miles per hour through a day of fishing, all for under £300.
5. Propane powered outboards
Another fast-growing alternative outboard fuel source is propane. Conversion kits allowing you to modify small carburated engines from gas to propane have been around for years, but in 2012 Lehr introduced a pair of outboards, 2.5 and 5hp, and more recently now in the UK a 9.9hp (15hp available in US), designed from the ground-up to run on propane. The advantages of propane over petrol are significant: stowed in a gas canister the propane is safer, and it burns much more cleanly. These engines run more smoothly than many two-strokes, are easy to start, and don’t require a choke or priming.
The down-sides? Although Lehr has been producing lawnmowers and other small propane-powered devices since 2008, their outboards simply haven’t been around long enough for us to judge long-term reliability. On top of that, while they are smoother than two-strokes, they aren’t as smooth as many four-strokes. And they’re a bit more expensive than traditional engines, starting at £729 for a 2.5hp model.
Finally, propane has fewer BTUs per gallon than petrol (between 10- and 30-percent depending on the formulation), and in automobiles, is less fuel-efficient by a margin of around 15-percent. However, according to Bernardo Herzer, CEO of Lehr, the loss of efficiency is explained by the fact that cars use converted petrol engines whereas the outboards are able to use much higher fuel compression ratios. "Converted gasoline motors are not getting the energy out of the fuel which is what happens when you convert a car motor to run on propane.”
Alternative power in boats isn’t limited to outboards. Ski Nautique launched its prototype Nautique-E all-electric inboard ski boat in 2011, utilising a pair of electric automotive motors marinised by LTS Marine.
Cigarette rolled out its AMG Electric Drive Top Gun last year: a 38-footer carrying 12 motors that feed twin stern drives to produce 2,200hp. With two tons of batteries in the hull, it can reportedly run for 30 minutes at 60 knots along with “a few blasts” to its top-end speed of 95 knots. Oh, yeah—and it only cost about £3 million to build.
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Chances are we’ll also see some different types of alternatives hit the market in the coming years. Greenline has been pioneering solar diesel-electric boats, with models like their Greenline 40. When submerged, Germany’s new Type 212 submarines operate on polymer electrolyte membrane hydrogen fuel cells. And we’ve even heard of new high-tech boats that use long carbon-fibre poles and acres of carbon fibre cloth to catch air currents, propelling the boat forward at speeds faster than the breeze itself! Of course, if propulsion problems were that easy to address, somebody would have thought of such a simple solution a long, long time ago.
For a brief presentation by the author of some of the main points above, click on the video link below:
For more renewable energy boating ideas see: Code X: the 47ft renewable energy speed machine and Vripack V20: The Start of the Solar Racing Revolution?