# 15kW electric motor for Sailing Catamaran



## caver22 (Apr 15, 2020)

Greetings,

Looking for advice on a 15kW 48V electric motor to fit to a Yanmar SD25 sail drive (new model of the SD20).

Application is an under construction 52' sailing catamaran. 

Some broad boat parameters:

Ocean going world cruising catamaran – composite epoxy structure.
L 52’, Draft 2’ Weight approx. 8500kg / 19,000lb
Full electric propulsion, galley and other services including hot water.
Motors retractable: 2 x 15kw 48v + regen
Battery bank: circa 16kw 48v 
House loads: 24V DC – Estimated peak approx. 3kw
Solar: circa 3kW.
16kW 48v DC gen set.

The plan is to fit motor to a Yanmar sail drive SD25 and complete unit be retractable. This involves a wet lower tube and a watertight inner tube with hull closure plate below the prop – motor and sail drive leg fitted to this at their join. We should be able to couple motor shaft to SD25 upper gear box shaft with a coupler and bolt units together without too many modifications. Be great to hear of others experience with this.

We are trying to limit motor voltage to 48V – makes batteries & solar easier plus ability to share bank via DCC converters & battery for house loads at 24V. 

The boat will be light and shallow draft = easily driven. A similar 62’ catamaran was fitted with 2 x OV SD15s and achieved over 9 knots in flat water so we believe 12 to 15kW motors will be adequate.


According to Vic Prop boat specs, twin 12kW (16hp) motors with RPM max of 2200 (2:1 gear reduction on SD25 so prop speed 1100 max.) & 3 blade 15" x 13" prop will yield a top speed of 8.92 kts which is fine.

We have looked at turn-key offerings from Bell marine, Oceanvolt & Electric yachts but none tick all our boxes so would like to have a crack at customizing our own solution.

Some motor options Ive stumbled across include:
1. Motenergy ME1302 or ME1616 Liquid cooled
2. Parker GVM210-100-DPW
3. Go cart or Elec motorcycle motors: Revolt, Zero, ???

Bearing in mind 48V supply and max RPM of around 2400, be grateful to get your thoughts on best motor and associated controller and any tips or constructive suggestions for our project.

Thanks RC


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## MattsAwesomeStuff (Aug 10, 2017)

How much do you want to spend?

Are you a thrifty person who likes making stuff work, or are you more of a "I want to spend the money and get it done" kind of person?


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## caver22 (Apr 15, 2020)

Hi Matt

This application is for an ocean going catamaran so needs to be bullet proof. Budget is not unlimited but generous. Regarding build I am an electrician by trade so comfortable with the wiring side of things, just no experience with DC supplied motors & their associated controllers. 

I think coupling the motor to the sail drive leg should be a straight forward engineering exercise that Im comfortable with.

The boat will be offgrid for 95% of the time and needs to be self-sustaining so we are limited to a DC bank of 48V. At this voltage we can get solar and a DC Gen Set to work effectively. Over this becomes problematic. Regeneration function is an important part of the energy mix.

There appears to be many motor options although less so at 48V. Max RPM needs to be 4000 or less to enable an appropriate propeller fitting so motor has to be efficient around the 2-3000 RPM mark. It also has be able to run continuously at say 70% capacity (say 10kW) without overheating. Liquid cooling is easy to arrange on a boat.

I saw a Parker motor that seems to fit our requirement. Im guessing there expensive but have no experience to judge whether they represent value or are the best option. Motenergy also a possibility ?

Hopefully this information gives you a clue. Appreciate your comments and suggestions.


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## macngee (Nov 27, 2014)

I don't know anything about converting boats, but I have seen kits on the Thunderstruck-ev website. It's worth a look. I've bought several HPEVS motor setups from them and they are good to deal with.



https://www.thunderstruck-ev.com/electric-sailboat-kits-and-accessories-inboard-motor-ev/


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## MattsAwesomeStuff (Aug 10, 2017)

Usually the cheap option is to grab a used forklift motor. You can usually get them for $200. They're bulletproof and functionally last forever.

In your case, since you're dead set on a low voltage battery solution, it might still be the best option since forklift motors are low voltage and slow.

For low power requirements, you might be able to get away with just reusing the forklift speed controller too.

You'll need to fabricate a coupler, but, this is no big deal.

Alternatively, you could buy something like a Gen2 or Gen3 Prius inverter, which has an onboard boost converter, and then use it to crank your 48v to 400v or whatever you want to use to drive the motor. Then you could use an AC motor which has nearly zero consumables (DC motors have brushes that will have to be replaced once every other decade or so, depending on use). I imagine that AC motors are better in marine environments, what with there being physical contact and corrosion potential for a DC commutator.


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## boekel (Nov 10, 2010)

A motor is not the problem, lot's of options available.

Any capable machine shop can couple it to a sail-drive leg (if I can do it..

I've done some testing with a Siemens motor on 48 volt, works fine, but the aluminium housing I would not use in a salt water setup (on fresh water it already deteriorates fast)

If you want to keep it simple: DC motor, air cooled.

If you want a little more sophisticated: AC motor, air cooled or water cooled. you might even be able to use it as a generator while sailing.

look for a commonly used 'standard' setup like the AC35 or AC50 HPEV motors:
https://www.hpevs.com/hpevs-ac-electric-motors-power-graphs-ac-35.htm
https://www.hpevs.com/hpevs-ac-electric-motors-power-graphs-ac-50.htm


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## boekel (Nov 10, 2010)

boekel said:


> A motor is not the problem, lot's of options available.
> 
> Any capable machine shop can couple it to a sail-drive leg (if I can do it..
> 
> ...


The costs are in the saildrives + custom machining, and the whole battery / charging / etc, the motors are not the expensive part, so best to get the most suitable available (and something that replacement can be found if needed)

'used forklift motors' is not what you want here, often difficult to find a replacement of the same size, and 15 kW continuous will need a big amount of old air provided to them.


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## caver22 (Apr 15, 2020)

Gents thanks for comments. 

Boekel your spot on regarding motor costs compared to the sail drive, engineering & batteries. Definitely worth researching and investing in the best motor for our application which needs to be a continuous rating at around 15kW @ 48v with max motor RPM 3000 

The HPEVS motors look interesting. I think the AC 34 or 35 would be more than adequate, perhaps even the AC20. Have had a quick looks at specs and output graphs and need to get my head around them. Assume continuous means just that and peak will be at max power for short periods. The peak amp ratings look extreme. Are these meant to be theoretical? 

In practice are these sorts of loads for short periods or are max peaks are programmed out of the controller to avoid system and battery melt down?

Presumably need to look closely at C-rating on batteries need to ensure they can deal with these sorts of current draws?

In a boat application we are more interested in continuous rating and the safety requirement to be able to run for long periods. As mentioned in my first post we have a 16kW 48V DC gen set + 3kw of solar to provide continuous power.

As the boat needs to be self-sufficient and generate its our power, have assumed that we would be limited to a max of 48V. The possibility of using a buck-boost inverter to increase voltage is intriguing but beyond my simple electrician's brain.

Regarding motor enclosure material, our motors will be located inside an engine room and so not exposed to salt water or even rain. The motor /sail drive unit be lowered via cutout in the hull when propulsion required and then raised out of the water into the engine room when under sail and not in regen mode.

Im surprised the HPEVS motors are not offered with liquid cooling since at low RPM, air cooling is reduced and heat build up may be an issue ? Boekel Im sure your familiar with the Bell marine motors which are from Holland and offered with air cooling for light duty and liquid cooling for commercial/ heavy duty applications.

Appreciate your comments - please keep them coming.


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## kennybobby (Aug 10, 2012)

The peak current specs on the motors are just for indication of capability--they could operate at this extreme current for a short time (5-10 seconds) without damage.

The motor controller (aka drive inverter, buck-boost converter, etc) would be configured to limit the current (torque) for your application.

Electric golf carts come to mind with low voltage motors in the 48V range. a quick search found some, but they are series DC motors with brushes;

i would want a brushless 3-phase motor if possible, such as PM or AC. Have you seen these: https://www.electricmotorsport.com/ev-parts/motors/brushless-motors?limit=all

Looks like an interesting and fun project, post up some pictures of your boat.


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## caver22 (Apr 15, 2020)

Some photos of our boat + a simple sketch of proposed engine retraction system.

Any further suggestions on motor types to research ?

Is it correct to assume that once a motor is selected, a suitable controller is matched and programmed by motor supplier to suit application OR do we need to get our heads around programming controller parameters as well?


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## SailorsRpblc (May 15, 2020)

boekel said:


> A motor is not the problem, lot's of options available.
> 
> Any capable machine shop can couple it to a sail-drive leg (if I can do it..
> 
> ...


Hi, I wane converted my sailboat 33feet to electric drive with driveshaft too. Can you please tell me what kind of siemens motor did you use? Thanks, and by the way nice work eith your outboard motor!!!


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## boekel (Nov 10, 2010)

SailorsRpblc said:


> Hi, I wane converted my sailboat 33feet to electric drive with driveshaft too. Can you please tell me what kind of siemens motor did you use? Thanks, and by the way nice work eith your outboard motor!!!


these:

https://www.diyelectriccar.com/forums/showthread.php/siemens-1pv5135-4ws14-motors-europe-202547.html


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## Solarsail (Jul 22, 2017)

caver22 said:


> Greetings,


I am not sure how you plan to retract the sail drive. But you should consider a pod drive where the motor is in water. See Torqeedo 10kW pod. The motor will be underwater and cooled. It is also direct drive, so no gearbox or angle gear box needed. You could then put two of these at the stern, to be retracted like an outboard engine. This allows you to remove the drive completely out, for maintenance, etc. You could even build your own pod drive.

You need more batteries. I would put in at least 50 kWh. 100 kWh even better. Chinese LFP cells can be purchased at $90/kWh. So $9000 will be a good investment. I would also go to 96 volts or 72 volts if you find such a pod drive. 

Also put in at least 6 kW of solar panels. This can be done with a platform built on top of the davit in the rear.

Don't count on regeneration. You are lucky to get 50% efficiency. Solar beats regeneration, except for cold climates.

Let us know how it goes.


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## Passedyouby (Dec 5, 2020)

Awesome build!!!

Any updates for us???


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## dbp (Apr 11, 2021)

caver22 said:


> Some photos of our boat + a simple sketch of proposed engine retraction system.
> 
> Any further suggestions on motor types to research ?
> 
> Is it correct to assume that once a motor is selected, a suitable controller is matched and programmed by motor supplier to suit application OR do we need to get our heads around programming controller parameters as well?


Nice, wish I had the space to build..
Since your building, hydrofoils would double your cruising speed and lower your amp draw, not to mention a smooth ride. ( Just a thought, since your in the building process ( it outs the saildrives but cheap way to extend the range).

You should cool your motors. If you can sleeve it and fill it with coolant or mineral oil then coil stainless tubing, place into pipe. Then run seawater through the pipe and out the hull to keep it cool without the corrosion to your motors. ( simple heat exchanger )

I would double the size of motors you think you need.. Most only run @ 50% before they start sucking the amps and the benefits are worthless speed vs amp draw at 100%.. Get something you can run @ 30-50%. Look at your motor specs and compare them. Treat it like a gas engine you can putt around at cruise speed or WOT. Fuel or Electric, she's gonna suck some juice.

As for rpms don't rely too much with rpms. *ie*. A10k motor might freewheel at 10k @ 0% load, but only using 50% and adding a load to it will bring it down further ( based on Amp Load ) you would need to gear final drive. With the sail drives you don't really have that option to control your amp/rpm, so your looking at a prop swap to match your motor.
Just pay attention to the motors spec sheets.

If your just sailing around the caribbean, I would try to gain as much power from solar with a smaller battery bank. If you can match motor output single or double, your going everywhere for free. Use your battery bank as a buffer between the system and a dc genset for backup power. 

Anyway I know this post is a bit old, just wanted to throw in a few pennies.. Would really like to see the progress on your build.. I hope to be doing the same thing in tens years, assuming my mast is still standing !


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## ElectroNick (May 1, 2021)

caver22 said:


> Greetings,
> 
> Looking for advice on a 15kW 48V electric motor to fit to a Yanmar SD25 sail drive (new model of the SD20).
> 
> ...


Hello RC,

Interesting to read...as I am exactly 'in your boat'...just planning to fit electric propulsion to a 48' aluminium sailing catamaran here in Scotland. Perhaps we could compare notes some day? My email is nick 'at' loening . com 
Do get in touch.
Best of luck,
Nick, Edinburgh, Scotland.


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## popobowa (May 4, 2021)

Hi caver322..nice boat project!
Heinzmann is a co. with the right product for you.
theres a motor with 18.5kW @3000 and 96V, PM brushless, at 6000rpm it gives more power but V is high.
measurements are compact too, very long srvice intervals 10k hrs.

One figure you can take as estimate for hydro regen. with a propulsor prop is app 7-10% of the actuator disc energy. Ive researched the options for various regen setups, also one using a sail-or OBdrive. 
If you want to be more efficient with regen you need a dedicated prop or at least a cp prop that can turn up to 120deg through the feathering pos. to the "other" side. As a regen prop has to produce torque, not thrust, the needed lift vector of the blades must be orthogonal ,90deg.,to boatdirection or thrustdir.

Iam also curious how you want yo solve the bottom plate thats covering the cutout when sailing. It woukd surely create a lot of drag when motoring?
Bette geather it. 
Also check out Bruntons Props, they got a new cp prop with computercontrol for various motorsail and regen scenarios.
The OV servodrive sounds good, IS expensive but has to be finetuned softwarewise...it didnt work at all on Jimmy Cornells Cat attempting to circumnav. the globe....chk youtube.

I would not try to regulate rpm too much but fit a voltageregulator...so you have to hang you sd leg of the back of a boat and see what voltage you get under which loads... then look for a regulator. Even a MPPT should work if within V /A bracket.

hope this helps...and lets know how you get on.
good luck


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