Choice of Motor for Small Boat

Boats, Jet Skis, Kayaks etc., including hovercrafts
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Jamiea
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Choice of Motor for Small Boat

Post by Jamiea » Aug 22, 2016 2:29 pm

Good evening.

I am thinking of building an Amp Eater boat (a 13' stitch and glue boat designed for electric power) and am looking into suitable motors. I plan to use it on calm, non-tidal rivers and wonder whether motors from electric scooters will be suitable. An example that is fairly available here in England is below.

HMParts E-Scooter electric Motor 24V 500 W Model: MY1020
Electric motor
24 volt DC (direct current) 500 Watt
Rated Speed: 2800 RPM
Rated current: 28 A

Is this likely to be adequate to propel the boat a tolerable pace?

Regards,

James.

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Re: Choice of Motor for Small Boat

Post by amberwolf » Aug 22, 2016 2:39 pm

How much power will it take to move at the speeds you need, with that particular boat, with the propeller you've chosen (if you haven't picked one, you can do so for the purposes of the calculations/estimates)?

If you're not sure how much power it will take, you might check with others that have used that boat design on what their usage is. Or there are some boat design/conversion threads here in this subsection that discuss it (not sure ifi they have the math directly in the thread).

Jamiea
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Re: Choice of Motor for Small Boat

Post by Jamiea » Aug 22, 2016 3:23 pm

How much power will it take to move at the speeds you need, with that particular boat, with the propeller you've chosen (if you haven't picked one, you can do so for the purposes of the calculations/estimates)?
I have not yet progressed as far as the propellor, to be honest. The outline information for the boat shows that it needs a 1/2hp DC motor. I suppose what I am really trying to ascertain is whether or not this particular engine is likely to be robust and sturdy enough to cope, as much as having enough power.

James.

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Re: Choice of Motor for Small Boat

Post by amberwolf » Aug 22, 2016 3:30 pm

If you mean mechanically well-made...it's a common brushed motor used on lots of really cheap scooters. So...there are a lot of them out there but I doubt most get used very hard to test them. Usually you pay for what you get....


So it will depend on how much power you have to get out of it, and how you set it up ot drive the prop. If you have to run it near it's max (or beyond) to get what y ou need out of it, it will probably have a shorter life.

If you are using a minimal amount of what it's capable of, it migiht last longer than the boat.

Until you know what you need out of it, it's hard to say how it will last for you.

Roughly 1/2hp is around 375w, so well within the motor's specs, but what RPM you need and how you then choose to gear t his motor up or down to get that RPM while staying in the motor's effficient speed zone, and how you keep the motor cool, will all make a difference to how applicable this motor is ot your project.


If you look the model number up here on ES you can see people that have used and abused it and see their results, in various land vehicles, that probably stay dry.

If you have to enclose yours to prevent it getting wet then it will get hotter and last less time, too.

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Re: Choice of Motor for Small Boat

Post by Ianhill » Aug 22, 2016 5:29 pm

I have drove a 36v 1000w version of this motor on 12s/50.4v at 60amp peaks so 3kw max and it has held together remarkably well but its revving at 4.8k rpm so it would be no good to directly drive a propeller as it spins to fast so what you would need is the 48v version and run it at 12v for a prop speed around 750 rpm with direct drive and then use a large prop so you can to make use of the low rpm and have decent push and speed don't use voltage convertors just get a pwm controller and run it off that but with out trial there is no error.

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Re: Choice of Motor for Small Boat

Post by Hillhater » Aug 22, 2016 6:02 pm

As a minimum, read this thread first..
https://endless-sphere.com/forums/viewt ... 39&t=19115
This forum owes its existence to Justin of ebikes.ca

Jamiea
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Re: Choice of Motor for Small Boat

Post by Jamiea » Aug 23, 2016 3:02 am

Thank you for the replies.

Ian: I am a little puzzled. I am probably missing something, but if I run a motor rated at 48 volts using just 12 volts, will it not draw a much larger current, resulting in shortened running time?

Regards,

Jamie

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Re: Choice of Motor for Small Boat

Post by Ianhill » Aug 23, 2016 3:16 pm

If you run the motor with a pwm board you can limit the max current (torque) and the pulse width (rpm), The 48v 1000w motor will have an efficent zone around the 400w to 800w mark I would run it at 12v ×30amps max and it would be very torquey and fairly efficent then for a brushed setup but I never even been In a boat let alone built one i'm a scooter man, The prop speed and size be key to make use of torque.
Personally I would do an old fashioned paddler with a few 900 c bike wheels and a set of brushless hoverboard hub motors be very efficient for a slow mover and have pedel assist not to get stranded on a lake or down the canal etc similar to this.
paddleboat-rental-1.jpg
Thinking about it the best setup would be a fwd so it will pull into the steer and maybe pedal assist rears for the straights and stranded or if your fancy all wheel drive and rear pedal assist.

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Re: Choice of Motor for Small Boat

Post by Jamiea » Aug 24, 2016 2:47 am

Ian.

Thank you.

James.

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Re: Choice of Motor for Small Boat

Post by major » Aug 24, 2016 9:04 am

Have you looked at trolling motors? They're made for the job and use the water as a heat sink. Have the correct prop directly shaft mounted. Might be your easiest/best solution. Typically many on eBay.

Jamiea
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Re: Choice of Motor for Small Boat

Post by Jamiea » Aug 25, 2016 3:19 am

Have you looked at trolling motors? They're made for the job and use the water as a heat sink. Have the correct prop directly shaft mounted. Might be your easiest/best solution. Typically many on eBay.
I had considered these, but want to use an inboard motor.

I have contacted the designers of the boat who felt that 500 watts would be adequate: they used a 1,000 watt engine which was more than enough. However, I have looked further afield for a motor and located some manufacturers in China who can supply single 24 volt, 1,200 watt motors, shipped and supplied for reasonable prices, so shall probably pursue that route once I am ready.

Regards,

Jamie.

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Re: Choice of Motor for Small Boat

Post by Hillhater » Aug 25, 2016 5:10 pm

I would repeat the advice to confirm what the optimum prop/rpms are , then find a motor to get close to that speed with the power/torque required.
Better to avoid reduction gears/belts etc if possible
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