Electric boat

Electric Boat is sometimes used as a colloquial abbreviation for the US Electric Boat Corporation. This article is about electric boats themselves, rather than this corporation.

Types

There are as many types of electric boat as there are boats with any other method of propulsion, but some types are significant for various reasons.

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• Historical and restored electric boats exist and are often important projects for those involved. See the Mary Gordon Electric Boat for example.
• River and lake boats. Electric boats, with their historically limited range and poor performance against a strong headwind or current, have tended to be used on inland waterways. In this environment, their complete lack of local pollution is also a significant advantage.
• Electric outboards and trolling motors have been available for some years at prices from about $100 (US) up to several thousand. These still require external batteries in the bottom of the boat, but by being a one-piece item apart from that, the manufacturers have been able to optimise the combination of the motor, the speed controller and the drive chain including the all-important propeller. Electric outboards have for some years provided an ideal drive system for inland waterway fishermen, being quiet and pollution-free so as not to scare away or harm the fish and other wildlife. As technologies improve, they should bring these benefits to many other dinghy users too, such as for yacht tenders and other inshore pleasure boats.
• Cruising yachts usually have an auxiliary engine, and there are two main uses for this engine. One is to power ahead or motor-sail at sea when the wind is light or from the wrong direction. The other is to provide the last 10 minutes or so of propulsion when the boat is in port and needs to be manoeuvred into a tight berth in a crowded and confined marina or harbour. Electric propulsion is ideally suited to the second case. The first case provides many - especially beginning yachtsmen and women - with a cause for anxiety, as a powerful diesel auxiliary has often been known to get a boat into harbour when sail power alone, or sail with limited help from an electric system, would miss the tide, the hours of daylight, or a rising gale. In fact with good seamanship, good passage-planning, sailing skills, the ability and willingness to keep to the deep sea or to anchor off in unfavourable conditions, none of this need be a problem, except perhaps for those in a hurry to get home, maybe for work in the morning or to feed the cats.
• Diesel-electric. There is a third potential use for the trusty diesel auxiliary and that is to charge the batteries, when they suddenly start to wane far from shore in the middle of the night, or at anchor after some days of living aboard. In this case, where this kind of use is to be expected, perhaps on a larger cruising yacht, then a combined diesel-electric solution may be designed from the start. The diesel engine is installed with the prime purpose of charging the battery banks, and the electric motor with that of propulsion. There is some reduction in efficiency if motoring for long distances as the diesel's power is converted first to electricity and then to motion, but there is a balancing saving every time the wind-, sail- and solar-charged batteries are used for manoeuvring and for short journeys without starting the diesel. There is the flexibility of being able to start the diesel as a pure generator whenever required. The main losses are in weight and installation cost, but on the bigger cruising boats that sit at anchor running large diesels for hours every day, these may not be too big an issue, compared to the savings that can be made at other times.