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Electric RC boat motors

Electric rc boat motors come in several different designs depending on the type of boat that the motor is going on.

The standard 'wound' motor with direct drive running hardware is the most common, but other motors and set-ups are electric outboard, hydrodrives and jet drives.
Popular sizes of electric motors for a typical RTR (Ready to Run) entry level rc 'sport' boat are the '500' or '700' size motor, the 700 being more powerful. Electric motors for rc boats do vary greatly in power but these common size motors are based on a 6 volt or 7.2 volt rc battery pack.

This is the most likely size that you'll find if you buy a RTR boat and it provides plenty enough power for the novice to learn on.

As you gain experience and find yourself needing more speed, you can upgrade the motor to a more powerful one.
This is usually a fairly straightforward task but you may need to seek advice before doing this; your local boat club or hobby shop will be happy to help out.

Below is a picture of a fairly standard electric rc boat motor set-up, showing motor, speed control and battery pack:


A typical electric boat set up


A recent development of the electric motor for rc vehicles is the brushless motor. Brushes are an essential component of standard wound electric motors and are the part most likely to need replacing first, as they wear out.
A brushless motor, as the name suggests, does not have these however and can deliver an enormous amount of power for their size, sometimes up to 300% more than their wound motor equivalent. Brushless motors are more expensive though, and are more likely to be used by rc boat modelers who regularly race in competitions.
A typical brushless motor is shown below right, alongside a standard wound motor:


Stock and brushless electric rc boat motors


Electric outboard motors aren't hugely popular in the world of entry level boats but are available for use on tunnel hull racers or where scale authenticity is required.
A popular example is the Kyosho Dolphin, shown below:


Kyosho Dolphin electric outboard motor


Everything is housed within the plastic casing, it's just a case of attaching the motor to the back of the boat and setting up the radio control linkages.
Again, an electric outboard motor will be using the standard '500' or '700' size electric motor.


Jet drives are a fairly recent addition to the world of rc boats. The principle difference is that no propeller is used, instead 'impellers' take their place.
An impeller is a very small multi-bladed prop that is located inside a duct. It spins at very high speed and sucks water into the duct from beneath the boat's hull and expels it at the rear of the boat at a very high speed, thus pushing the boat along.
Again, a typical jet drive for an electric rc boat may be powered by a 500 or 700 size standard electric motor.

Rudders aren't used on rc boats that have jet drives, as the steering is controlled by directional movement of the jet drive and hence the jet of water. An example of an electric rc boat jet drive outlet with 'reverse buckets' is shown below:


Jet drives




Speed control for electric motors

All electric motors require some kind of speed control, these can be either mechanical or electronic.
A mechanical speed control requires the use of a servo to operate it, whereas an electronic control plugs directly into the receiver of the boat. These are by far the best and most widely used in electric rc boats, as they offer precise control of the motor and are completely maintenance free with no setting up required.

An advantage that an electric rc boat with an electronic speed control has over a nitro model is the ability to reverse. Not all speed controls have this option, but the majority of them do, and it can be a nice function to have if you find yourself stuck against something and going backwards is the only option!


Water cooling an electric motor

It's worth noting that the more powerful the motor, the hotter it will get while running. This is bad news; prolonged and excessive heat can result in the early death of the motor by 'burning out'.

For this reason you may need to buy some kind of water cooling kit. These consist of a length of plastic or silicon tubing, sometimes pre-coiled, and an intake and outlet valve. A small hole just big enough to take the intake valve is drilled at the rear of the boat, usually just behind the prop.
A second hole to fit the outlet valve is drilled somewhere in the side of the boat close to the motor. The tubing is then attached to one of the valves, coiled around the motor and attached to the other valve. As the boat speeds along, pressure forces water up the intake valve, through the tubing and out through the outlet valve.
As the water rushes round the motor, it takes alot of heat away from the motor and helps keep it much cooler than it would otherwise get.

 

Related pages

Electric RC boats - getting started info and some examples.


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