# Motors in Boat



## jhuebner (Apr 30, 2010)

Sounds like a job for regular AC industrial motors with some sensorless industrial VFD. They're built for 24/7 applications.

That is if you plan on a ~300V generator and battery bank.

The motors can be hacked to run with 1/2 or 1/4 of their nominal voltage, if you feel like fiddling around a bit.


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## Motorboat (Feb 5, 2015)

Thanks for the info sir, ill look into that.


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## Duncan (Dec 8, 2008)

Hi Tom
Have a search some other people have done the same
At low speeds you don't need a lot of power in a boat,
My forklift motor is rated at 10Kw continuous (I put up to 100kw through it) 

Props
biggest you can fit (most efficient) - bigger = slower should be able to run direct drive


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## Karter2 (Nov 17, 2011)

You do realise that 8-10 kW. Generator once it has been through an inverter etc, is going to give you about 10 HP max at the prop !
How well do you think your 32ft planeing hull would go with a 10 HP outboard on the back ?.?
My guess ?....slow, 5-6 mph max !
It would be much better /simpler/more economical to run,...if you installed a simple direct diesel prop drive


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## Motorboat (Feb 5, 2015)

Well, as i said i dont expect to get this hull on top however i know its possible. Like i said im in the preliminarys of this, however for example there are commercial fishing boat in the 25 to 35ft range in Asia now running over 20 knots loaded. The technology is here, just have to do the research and number crunching to make it work. Im sure of it. As far as the single diesel goes, i have thought of that however to be frank ive been running diesel boats for years and am tired of the maintenance noise fuel costs and general upkeep of them. 

Check this link out for the latest on this. Electric fishing boat - Leo Greentier Marines (LGM) (youtube)


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## Karter2 (Nov 17, 2011)

Yes but there are 35' hulls and 35' hulls.....not all the are same shape.
And a planing hull is one of the most inefficient when being driven at displacement speeds...all wetted area, and no "flow" finesse. Lots of drag.
... Diesel maintenance, noise and fuel costs ???...
....but you plan to be using diesel generator(s) to power the electrics anyway !
You will just be using bigger less fuel efficient, diesels, with a much heavier and costly drive system,....than if you cut out the electrics and went direct Diesel !
What are you expecting to gain from this approach ?


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## nimblemotors (Oct 1, 2010)

Might I suggest you sign up on the electric-boat-forum.com where the details can be shared with others thinking of similiar projects.

A slow going boat is actually quite good choice for electric propulsion, unlike a car that can't go 5mph to get long range, a boat can!
Are you sure you want to go so slow with what sounds like a fast 32ft speedboat? 

Have pics?


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## RIPPERTON (Jan 26, 2010)

The Diesel sounds like your only problem so don't do a Diesel.
These rotarys look like they don't even have sumps.
http://www.freedom-motors.com/index.php?option=com_content&view=article&id=98&Itemid=80


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## Motorboat (Feb 5, 2015)

Im well aware of the hull's disadvantages. Like i said i'm not looking to get this boat to plane. Its very simple, the gas 350's burn 25 gallons per hour to run, about 250 gal a day for a blast offshore at 17knots if im lucky. I would say thats a pretty inefficient if you ask me. So what if it takes twice the time to get out there, ill go the weekend instead of pounding out there and back in one day. ImA take it easy.. headin over to e boat forum, Thanks for the info fellows


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## Duncan (Dec 8, 2008)

Hi Motorboat

Each time you convert energy the gods of thermodynamics take their cut

Diesel fuel to mechanical power
mechanical power to electricity
electricity to mechanical power
mechanical power to "thrust"

Using a diesel direct to the prop takes 2 and 3 out of the equation 
and is more efficient

From what you are saying the problem is that cruising at speed requires too much power (money)
The solution is simply a lower speed and a smaller diesel engine

If you only need 15Hp then get a small diesel gear it down and drive a single prop
(bigger is more efficient when it comes to props)

It may even be sensible to keep the big engines for emergency use - sometimes too little power is dangerous


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## Karter2 (Nov 17, 2011)

Motorboat said:


> Im well aware of the hull's disadvantages. Like i said i'm not looking to get this boat to plane. Its very simple, the gas 350's burn 25 gallons per hour to run, about 250 gal a day for a blast offshore at 17knots if im lucky. I would say thats a pretty inefficient if you ask me. So what if it takes twice the time to get out there, ill go the weekend instead of pounding out there and back in one day. ImA take it easy.. headin over to e boat forum, Thanks for the info fellows


Let us know the feedback.
It may take you much more than twice the time to get out there, you may not get there at all !
8kw from the genset won't give you the power to run against tide and wind with that hull and freeboard. Barely enough power to manoeuvre safely in strong conditions .


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## nimblemotors (Oct 1, 2010)

well, let's see..if you are going 5 miles an hour, then you can go..wait for it..
5 miles in an hour. That is 20 miles in 4 hours. 

The trip to Catalina Island from Long Beach is about 30 miles.

There are people who will take you on their sailboat to Catalina, and you should plan for a 6 hour trip.


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