10KW Brushless Sailboat Kit



Convert your 12-29 HP diesel engine to clean, quiet electric. Eliminate noxious diesel fumes and the frustration of filling up at the pump with the 10KW Brushless Kit featuring a Motenergy brushless motor and a 48V 450 Amp Curtis AC-F4 Controller that can produce up to 10KW continuous, often used to replace <30hp combustion engines!  Enjoy your sailboat to the fullest, with a silent drive and truly fresh air.

This system is recommended for boats up to 12,000 pounds displacement. All our systems have reverse on-the-fly and contactor disable features. "Brushless" means that the motor does not have brushes that will wear out over time, nor will it be a dangerous source of ignition for on-board gas appliances. Larger boats may require a higher power AC or brushless motor. In the U.S. and Canada, brushed motors are only legal for marine use if onboard appliances and accessories use kerosene or diesel (not propane or gasoline) due to the potential for internal motor arcing.

With Curtis' AC-F4 controller, no reversing contactors are needed. Additionally, the Curtis controller has a regen feature than can allow current to be put back into the batteries from the spinning prop while under sail. This does depend on your sailing speed, prop design, and may not be possible in all applications, but is an adored feature for those who are able to utilize it.

A Gear Reduction is not always necessary, and largely depends on the size, efficiency, prop style, and desired speed of your vessel. However, due to the high RPM of the Motenergy Brushless motor, we recommend you consider a gear reduction rather than direct-drive to improve efficiency, provide proper torque, cooling, and help prevent cavitation. Typical reduction is around 2:1, but this ratio will depend on the required prop RPM needed to reach hull speed. Ideal reduction will enable the motor to spin your prop at the hull speed RPM of your prop when the motor is spinning at its max RPM. This number can be calculated using the 50 RPM / Volt constant:

48 Volts * 50 RPM / Volt ~ 2400 rpm max

What about Batteries? Most customers are happy with sealed, deep cycle lead acid, sourced locally to save on shipping. Use 4 in series to get 48v and 100 amp hour capacity minimum. Larger capacity will give a longer run time.

If you choose not to use a gear reduction, it's important to install a thrust bearing somewhere in line with the prop shaft, as most motors are not rated for axial/thrust loads on the shaft. Also note that a heatsink for the Sevcon controller is recommended by the manufacturer.

Kit includes:

  • Motenergy ME1115 Dual-Stator Brushless Motor
  • Controller: 48V Curtis AC-F4
  • Throttle (additional cost)- your choice of: 
    • ET-134 directional throttle. For harsh environments we recommend the ET-134 as the most robust option. Use the ET Actuator to connect to your existing throttle cable. ET-134 has a Neutral Detent, ET-126 is Spring Return. 
    • Wigwag throttle lever if Not reusing your existing lever
    • PB-8 throttle and Fwd/Rev Switch
  • Tyco High-Quality Sealed Contactor
  • Key Switch
  • Fuses
  • 200a Breaker
  • Every kit is individually bench tested
  • Complete wire harness with 10ft key and throttle cable lengths
  • Wiring instructions

Helpful links:

Check out our instructional wiring video!

You may also be interested in the CAN Translator

Those of you that are still in the "research phase" of your conversion should visit one of the electric boats discussion groups and talk to others who are doing or have already done electric conversions.

Gen4 10KW Sailboat Kit Wiring Diagram - for Fw/Rev Switch Option

Gen4 10KW Sailboat Kit Wiring Diagram - for Curtis ET throttles

Gen4 10KW Sailboat Kit Wiring Diagram - for Wigwag Throttle

Gen4 Sailboat Kit Installation Instructions

Gen4 fault codes

E-Boat Modeling Spreadsheet (.xls) *Use this to calculate your power needs!*

E-Boat Modeling Spreadsheet Manual (.doc)

Vicprop Calculator

Using our charger w/ Solar


I put this kit into a 1991 Beneteau First 310 using a 2:1 gear reduction and powered by four Lifeline GPL-4DL (210ah) batteries. I can travel about 4.5 kts into a light headwind for about 3 NM and still have 85% battery left. Mathematically, that gives me a range of 20NM at 4.5 kts. I've never actually pushed it that far, but I have travelled 10 miles regularly and had about 50% battery left according to 2 different meters. Everything worked as advertised and tech support when I needed it was great. I'm very happy with the product and company.

And here is a find I didn't expect. I find the ability to spin the motor at really low RPMs amazingly useful when waiting for bridges to open up or while trying to remain "in line" at the locks in Seattle. With low throttle I can basically hover in place instead of having to drive in circles or forward and reverse constantly like the other boats around me do.

The one downside is that your amp draw goes up a lot (like 25-30%) if you are motoring into a strong headwind. So as a positive, the electric motor has gotten me to sail when I used to just motor because it's now actually faster to sail or motorsail into a headwind than try to motor straight upwind.

I can't tell you how happy I am not smelling diesel, or worrying if the engine would start, changing oil, fuel filters, air filters, antifreeze, cleaning spilled oil from the bilge, sorting out alternator issues. Oh... and it is so much quieter than a thumping diesel!
Installed the 10kW kit (with 2x gear reduction) in my 1984 Catalina 30 (replacing stinky, noisy original 11hp 2 cyl Atomic diesel).
Installed two Tesla 2.6375kWh (516 cell) batteries and charge with Magnum Energy 48V inverter/charger. Approx. $6.5K for everything.
Had to adjust the engine mounts twice to secure the shaft alignment but otherwise trouble free, quiet motoring with more power than before.
Its been more than a year since I installed the 10kW motor with the stainless steel Thunderstruck speed reducer mount in my Pearson 36. I highly recommend buying this mount and going with the 2:1 reducer.

Our Pearson 36 displaces 13,500 lbs. so its not a lightweight race yacht.

After 1500 nm of coastal California sailing and motoring, I feel we have enough experience to provide a reliable review.

We could not be more satisfied with the installation. We used four 48 volt Chevy Volt batteries (Ebay) for about 180 amp hours of storage. This equates to about 5 hours of motoring at 30 amps without taking the battery down too far. At 30 amps we motor at 3.5 to 4 knots in San Diego Bay - 3 knots in bumpy water - and we don't sail in hurricanes.

We often "motor-sail" in low wind conditions - using about 15-20 amps just to keep the sail shape. It makes the difference between slogging along at 3 knots and hitting 4 to 4.5 (for us that's an acceptable low wind speed).

Getting in and out of the slip, we find the electric motor to be very responsive. Getting underway consists of turning the switch on and pulling on the throttle. In that way, electric motors are superior to engines.

No engine maintenance, no fuel to buy (the 48 volt solar panels recharge the battery back in a day or two) and less noise. What's not to love?

I changed the belt this month because I felt bad for not doing any maintenance for over a year. It looked fine, but now I feel like a better skipper.

In Summary: If you are thinking about repowering, buy this kit.

Incredible kit for converting my 30' Catalina sailboat. This kit was quite easy to put together and has unbelievable power. I've connected a 48v Lithium kit from a Nissan Leaf and it it runs quiet, smell free and has lots of power.
The cheap ($500) battery keeps my 30' Catalina (10,500lbs) running for about an hour at low speed (
Bought and installed this motor 3 years ago now. Could not be happier! Quiet, reliable and simple! It replaced 19hp Volvo MD2020 in Nordica 30 sailboat. Batteries maintained by Airex 48v Wind generator, while boat is on a mooring.
Great support by the company, good instructions and guidance. I designed and built my own reduction drive 1:2 ratio, driven by toothed belt and pulled.
I have a 37 ft sloop and 48v system using 15kwh of LiFeP04. Very happy with it. I can go all day at 3 or 4 kts, and take it up to 5.5 kts when I need it. No smell/fumes, no maintenance, little sound, and I never have to visit the fuel dock. It doesn't get any better than this!
We have a Tartan 27-2 which has about 8000 lbs displacement. I did our conversion about 6 years ago, and am happy with the results. We have about 4 hours of range... Things like docking become much easier because of the better rpm control. Support from Thunderstruck has been excellent. Electric is not for everyone, but for our use which involves minimal motoring, it works great!
I have a 1976 Islander I-28...I installed the 10kw Thunderstruck motor, 2:1 gear reduction, Clearview Display, along with 8x Trojan T-105 batteries a year ago and couldn't be happier. It replaced the seized up Volvo.

The only issue was my propshaft was 3/4" with a non-standard 1/4" keyway...just make sure you measure your keyway as well as shaft diameter and let Thunderstruck know.

Otherwise install was pretty straight forward and have had no issues. Furthest we have motored so far has been about 16miles at 3.5knots. The majority of the time we return to the dock with +90% battery remaining. Motor is super quiet and we would do it again in a heartbeat.
We really love the electric motor [Ericson 32]
I have been happy with my 10KW Sailboat kit for a year of use now.
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