Efficient inboard electric drive available

5.5Kw motor in Kapowi

Since I started the Torqeedo Shop I’ve been researching inboard electric drives so that we could offer a range of electric boat solutions. I’m now convinced that the systems from Propulsion Marine of Santa Barbara, California, are the best available for boats in the 24ft to 35ft range and we have struck an agreement with James Lambden to be able to offer their motors downunder.

What you get in the package

A 5.5kw unit will be shipped to us soon and I’d like to tell you a something about why I’m impressed by these motors. The total system has been developed and proven on James own 30ft boat, Kapowai, so he’s made sure that all elements of the package have more capacity than what they’ll be called on to handle. Heat dissipation is critical for electric motor efficiency and to be sure it runs cool Propulsion Marine use twin stator motors which means the motor can run all day at its rated power of 5.5Kw. When you’re comparing electric drives be careful to check that the claimed power of a motor is a continuous rating and not just a a power setting that it can only maintain for a short surge. As a guide, this motor is capable of 10kw surges such as you might use when manoeuvring or to get clear of a oil tanker bearing down on you.

Clearview displays useful motor data

The programing used in the Sevcon controller of this package has been developed especially for Propulsion Marine and is characterised for the usage profile typical of a yacht. Controllers designed for use in road vehicles and forklifts don’t always adapt well to the special requirements of a marine engine.

We’ll be offering this first unit for an introductory price of $6450, and I think we’ve estimated lightly for import costs so once we bring this one in we’ll know for sure and we’re expecting to set the price a bit higher than this. The 5.5 Kw unit will offer similar performance to a diesel engine in the 15 – 25 hp range. So if you’re wanting replace an aging or broken diesel of that size now is the time to think about switching to quiet, odour free propulsion.

Display model with prop

To get best efficiency for electric boats (and any boat really) its important to match the prop carefully to the motor. So we’ll also have a prop available to match the motor gearbox combination and that would suit a yacht around 30ft.

Kapowai motor sailing in light winds

The prop will be $500 bringing the price for the package to $6950.00. Talk to us about whether your existing prop might suit. As general rule, a larger diameter, larger pitched prop turning more slowly is more efficient and if a larger prop can be fitted in the aperture its worth upgrading.

Just as the Torqeedo motors use a reduction gearbox to multiply torque, and be able to swing a much larger propeller than you’d expect, so with the Propulsion Marine packages. By using a gearbox rather than a toothed belt you have a more compact package with very low gearing losses. Its not always possible to choose the best gearing for a particular boat on the first try. So we’ll swap gear ratios for you at no charge so we can maximise the efficiency of your setup.

See the chart below for a guide of the kind of speed you’d expect from a boat around 30ft. We can help you choose the correct propeller and gearbox reduction for maximum efficiency of your boat.

For comprehensive background information we recommend Propulsion Marine’s electric boat design site. For details of other Propulsion Marine products go to their site here.

Power vs boatspeed for Kapowai

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