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15kW electric motor for Sailing Catamaran

12193 Views 16 Replies 11 Participants Last post by  popobowa

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 DC:DC 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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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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