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Emergency electrical power

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What is the issue?
If you flatten your battery, unless it is a particularly small engine that can be cranked over manually, you will be without engine power and be crippled for power aboard. This is a very bad occurrence whilst out in deep ocean or in a remote location whilst long distance cruising.

Why address this?
Discharged batteries will make the vessel completely dependant upon its sails, and places instrumentation and navigation lights in jeopardy. In certain situations this makes for hardship, and could develop into a situation where the vessel could be lost. Even in well-sailed waters, UK organisations such as the RNLI will tell you that the vast majority of their calls for assistance are engine related.

How to address this?
A small portable petrol generator aboard may be worth its weight in gold in this situation. Discharged batteries can be replenished in a reasonable amount of time.

But a small generator is also a very useful item to have aboard a boat from day to day. It can be useful in a variety of roles and will earn its keep.

They generate a fair amount of power in a small space and can be fairly fuel efficient. Petrol powered generators typically use between 0.25 and 1 litre of fuel for every hour that they run, and can easily power a 25A or 40A battery charger. It is far more efficient to run it to charge the batteries rather than the main engine for the occasional top up, and never more so than during the 'Absorption' and 'Float' stages - see care and maintenance of batteries Experience.

Likewise, If you include just these three tools with the generator you can dramatically simplify an on-board repair and development whilst cruising:

  • (i) A 100-125mm angle grinder. An angle grinder, also known as a side grinder or disc grinder, is a useful handheld power tool used for grinding, abrasive cutting and polishing. They are used with metal cutting blades but accept a wide variety of cutters and attachments such as a sanding disc, grindstone and wire brushes, which make them very useful for a wide variety of purposes.

  • A 100-125mm angle grinder
    Photo: Michael Harpur

  • (ii) A jigsaw. A jigsaw is a saw which uses a reciprocating blade to cut irregular curves, such as stencilled designs, in wood, metal or other materials. But it can be turned to be an all-purpose saw for most boat purposes.

  • Compact Orbital Jigsaw
    Photo: Michael Harpur

  • (iii) Random orbital sander. Random orbital sanders are hand-held power tools for sanding in which the sanding blade delivers a random-orbit action. Because of this random sanding action, the tool does not leave swirl marks and is not sensitive to the direction of the wood grain.

Compact Orbital Sander
Photo: Courtesy of Bosch

If you are familiar with cooler latitudes, you will find the tropical environment surprisingly debilitating when it comes to any form manual labour. It is utterly amazing just how slow progress can be and how little can be done when it gets humid and hot. Most cruisers will tell you, when all is said and done, there is a lot more said than done in these environments. Power tools will make a dramatic difference to the tasks that may be successfully taken on and accomplished.


The above and below Honda EU1000i/EU2000i generators are quite popular amongst cruising sailors because they have a reputation for being quiet, reliable and efficient. They come in 120V AC and 240V AC versions. But there is a host of options available from a wide range of quality manufacturers and here are some quick notes from my personal experience.

Honda EU20-10i type generator
Photo: Michael Harpur

Stick to a 4 stroke for reliability and try to find one with an intelligent throttle that responds to the current loading and helps save fuel. Variable RPM generators, otherwise known as inverter gensets, create 3 phase power which is rectified to DC power internally and then inverted to a fixed AC voltage and cycle afterwards. They generally create a better stable sine wave output and their fuel consumption is lower than a fixed RPM generator. This is much better for sensitive electronics such as laptops etc.

Watch the weight as they do have a concentrated weight approaching 30KG that can be heavy to hump about the boat. Go for a minimum of 2KW. I first purchased a 1KW version but simply found it too small to support my powerwasher and 1.2KW kettle. 2KW - 3KW seems ideal but watch the weight. For any larger capacity onboard generator, a fixed diesel genset is usually preferred.

Run it every couple months to avoid fuel drying up and blocking the carb. Service it once a year with the normal amount of usage.


Graham Watts of the United Kingdom Boat Safety Scheme said: “On too many occasions we hear of fatalities or near fatalities on boats caused by the incorrect use of portable generators''.
Gensets emit deadly carbon monoxide
Photo: CC0

You cannot keep your portable generator inside the cabin or below deck. This is because they require a lot of ventilation. Gasoline powered generators emit carbon dioxide exhaust fumes and therefore it is not safe to keep them in a contained area. They must never be used where exhaust fumes could enter the boat and where they can cause injuries or fatalities. If exhaust fumes are detected in the boat, it could mean the cabin is also filling with deadly carbon monoxide. Genset should never be installed permanently or have unauthorised modifications that are not supported by the manufacturer, or proprietary component supplier.

Portable generators are very handy for providing power to a vessel while it is at its moorings. They are not designed to be used on deck on a moving boat and an inboard generator or the boats main engine should be used for this kind usage.


Some final parting words. I may be a little biased in my fondness for a genset and this comes from one incident. I came very close in the Indian Ocean to losing the engine due to battery discharge.

We were having a rough ride and were forced to hove too many times to deal with violent and challenging squalls that hit suddenly and turned the wind around 180°. Little did I know at the time, because we had not got a swan neckwe were unwittingly taking water down the exhaust outlet and down into the engine when laid over hove too. Suffice to say after coming out of a prolonged session we spun the engine over and over and it would not start. We believed it was lost and we had run out of battery power to turn it over again. It was literally on the very last gasp of the battery that our reliable engine coughed and then miraculously sprung to life.

We drew deep breaths and thanked our lucky stars for that moment as it was on the very last turn of the key. I started to consider what would have happened had that engine not started at the last moment. Very shortly at Galle Harbour in Sri Lanka, I was about to discover two possible outcomes. Two other boats that departed with us to Sri Lanka had battery discharge problems on the trip.

The first was a solo sailor who could not start the engine two weeks out in the highly unpredictable conditions we experienced. As the area south of Sri Lanka is a major shipping area she had limited power for navigation lights, VHF and instrumentation. This forced her to stay practically awake for two weeks trying to dodge and sail her way through the weight of shipping that turns the very busy corner. Completely fatigued she made it to 400 metres off the entrance of Galle harbour and was practically within the walls. Just then the wind died and within twenty minutes the surf pushed the vessel up onto the reefs. She clambered out to the shoreline under Galle fort but the vessel was a total loss.

A second boat had a solid crew with more good fortune. They lost all power because the batteries were low on water as a result of having been over-cooked by a charger in the marina prior to departure. Shortly after departing they came to realise the problem when the engine could not be started and not long afterwards the batteries degraded to a point where they lost all electronic instrumentation. This brought the vessel back to 19th Century sailing techniques and hardships for the passage but they got the vessel in.

In both these cases, the situation could be made dramatically better by having a generator and some petrol. Since that Indian Ocean experience, I have placed a generator on my list of cruising essentials.

With thanks to:
Michael Harpur, Yacht Obsession.
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