# Budget Electric inboard



## bmacfarquhar (Jan 12, 2010)

I read with some interest the extensive thread on putting a golf cart type motor in place of an inboard. Someone threw out the idea of a motor for $450, a charge controller for $150 and 4 golf cart batteries for $400 as a bare minimum docking power solution. I completely understand the range limitations and limited usefulness of such a setup and do not want to discuss comparing it to fossil fuel alternatives.

I just want to iron out the bare minimum components to get say 3-4 horsepower and a half hour or so of run time. Let assume you kept the stock prop and shaft that came with the original Atomic 4 setup. How would you create the drive linkage to the original shaft? Some sort of belt/ gearing? Are there pre-existing kits or parts for this purpose that are cheap? Anybody have some plans for how to build such a linkage? I'd prefer to use off the shelf parts from other applications then pay someone an arm and a leg for the same parts with a sticker on it. If anyone has any ideas I'd greatly appreciate them.


----------



## newpbs (Apr 21, 2008)

*Motor Controller*

You didn't mention the need for a motor controller. Electric motors have a great deal of torque right from the start. A motor controller helps to ease the motor rotation from a dead start. It will also provide you with reverse rotation. A simple on/off switch with a reversing circuit will not do it.

Paul


----------



## Architeuthis (Mar 3, 2008)

Ahhh I lost a long post. Here is a summary

Starter motors, cheap and powerful. Simple control, a push button to a relay. the bendix drive engages shaft, releases when done. Short duty cycle offset by using more. Consider liquid cooling, hey it worked for my computer.

Trolling motors.

Then basic 48VDC system. Electric Drives

Adapt an electric car kit.

Then an AC drive with electronic controller.

Personally I would suggest starting with trolling motors, cheap way to get into it with minimum cost/effort.


----------



## tager (Nov 21, 2008)

Those small trolling motors can get a boat going alright. I would suggest it too. Worked okay on my 3000 pound boat.


----------



## bmacfarquhar (Jan 12, 2010)

Architeuthis - sorry you lost your post it sounded like you had a lot of great ideas. Are you suggesting using starter motors as the main motor? What sort of application of starter motor would be powerful enough and are they designed to run for more than short periods of time?

I've considered the trolling motor option but they seem tiny unless you get the Torqueedo and then they seem overpriced... I've seen people stick an e tek motor on an old outboard. 

I was particularly interested in figuring out how to connect an electric motor to the existing prop shaft if anyone had done something like this and might have a photo or drawing of how they did it. I will look into electric car kits.

Electric trolling motors may work I am still looking for my boat have a short list and will be buying soon but the exact length and displacement are yet to be determined.


----------



## klem (Oct 16, 2009)

A trolling motor will be by far the cheapest but it is also the least powerful and not an inboard. If you go the inboard route, there are tons of little costs that will add up like wire, motor mounts, belt, sheaves, contactors, etc. On each of the electric vehicles that I converted, we counted on about $10k for the electric conversion parts. These systems are about 20kw continuous which is significantly more powerful but there are some serious economies of scale in things like controllers and chargers. We also did all of the fabrication on our own which is a big cost saver.

Hopefully someone can chime in with more current numbers since it has been a few years since I priced this stuff but it isn't super cheap. You can pretty easily go online and spec out the big components of the system to get you in the ballpark.


----------



## Mechsmith (Jun 7, 2009)

Starter motors are very short lived. I have used trolling motors for getting in and out of a marina but they can't handle much wind or tidal flow.


----------



## Mark F (Mar 7, 2006)

Hi bmacfarquhar,

It depends what boat you end up with. A (big) trolling motor has worked for me with a 23 foot - 3000lb boat. That was a 36 volt 105 lb thrust Motorguide. I repowered that boat 5 years ago and it is still running strong - as far as I know, I see it go out quite often.

My current boat an Ericson 27 (I'm sure you read about it in the thread you mentioned) has a "factory" built inboard unit. I was thinking about fabricating a system myself but decided I wanted something that was engineered and tested for function and a saltwater environment. I'm glad I did. 

I've got about $6000 dollars in materials into my electric inboard which includes; motor/motor mount, controller, battery monitor, all cables and switches for batteries, eight 12 volt AGM batteries and two chargers.

That system gets way more performance than you are talking about but I think you might outgrow a 1/2 hour range package pretty quickly.


----------



## Architeuthis (Mar 3, 2008)

*All glory to the starter motor (bow now).*

Few people realize what evil power lies under the hood of the lowly gas powered car. It isn't the internal combustion engine whose power is merely fire contained, it is the starter motor, a direct tap into a fundamental force of nature.

The evil power of the starter motor is kept under control, harnessed to do our bidding, but do not underestimate it. It is the motor of supervillainy.

For many a child their introduction to this demonic device is not from the family car, even if their family has a car, it is from the world of soap boxes and go carts.

Every kid has a soap box car, little more than scraps of wood nailed and tied together with which they hurdle themselves down every hill in town. The thrill of the ride, no matter how short, fires the desire for more, a desire for motive power.

For the rich kids this was supplied by a Briggs and Stratton, for the middle class an old lawn mower engine might do the trick but for the kid from the family with push mowers those solutions were too expensive.

Enter the starter motor.

Every old car has one and for the lucky kid he might get one from an old Ford with 460 cubic inches of fire controlling engine. That starter motor with its simple relay control system is easy to adapt and most important it is cheap. That aspect of the motor, its low cost, will be just one of the promises all electric motors make but somehow never really deliver.

The cheap starter powered soap box becomes a go-cart and that means racing the rich kids with their shiny ICEs. All it takes is the drop of the flag and the flip of the switch to unleash the raw power of the starter motor.

The wheels spin, grab and throw the cart forward as though Thor himself was pushing. The acceleration is the first time that kid actually feels the whole seat pushing against him, feels a surge of addictive adrenaline and the evil power of the starter motor. The starter go cart always wins the launch.

Then the evil fails as the rich kid slowly putters off into the distance. Like a candle the Brigs and Stratton just keeps on flickering, pitifully, yet continuously, claiming a weak mocking victory.

But the Starter motor is like the blinding shock wave of a Supernova. It dumps all its power in one huge burst and promises more if only it could have its insatiable need for electricity fed.

Later that kid will learn the math behind his starter motor, that it is a DC series motor in disguise. When that kid learns the theoretical ideal limit of such a motor is infinite RPM, infinite Torque, and infinite Power, the evil super villain is revealed and seen as a potential tool for world domination.

In practice the path to world domination via a DC series motor is littered with the many pitfalls of friction, heat and internal battery resistance. Even when one gets a mount that will hold the torque of pure evil unleashed, feeding that evil creates a treadmill of every increasing heat sinks, cable sizes and battery banks.

The siren call of a series DC motor with a simple relay control system unleashing infinite power has been the downfall of many. The promise is so very tempting, so very aluring but I would suggest another path.

If one can break from the lure of series power I would suggest they take the lesser path of the shunt wound DC motor. In that motor the pure evil is diluted, weakened to a point that it becomes safe and easy to handle.

From there a step back into evil can be had with a compound DC motor. A motor that harnesses the hellish power of the series winding but is more suicidal than world dominating.

As one progresses through the various drive motors and controllers you will often be reminded that all these steps, extra windings and circuits are needed to control the evil power that resides in all motors.

An evil power the lowly and cheap starter motor is ever willing to release.

So do take advantage of the starter motor with it's built in gear system and easy to adapt ring gear but be warned, cheap power can have a very steep price in time and money. It may even cost you your very soul. (not to mention any hope of getting a girlfriend)


----------



## nickmerc (Nov 2, 2008)

To answer the OP's question about using the existing shaft and prop...

Quick background; I'm a mech engr and design machines for a living. I am a big fan of timing belts.

You can get the belts and pulleys off the shelf from any industrial supply outlet. One of the big advantages of a timing belt system is you can cheaply adjust your gear ratio by changing one or both belts. Also, timing belts are around 95% efficient at transferring power. Some are better and some worse. Also, they last for a long time. Look at your car. My owners manual says I need a new one ever 100K miles. I streatch it to 120K. I just put in my third one.

The most important part of retro fitting a belt drive to your exising shaft is making sure the shaft is properly supported with bearings. The A4 arrangement is depending on the transmission to support the end of the shaft. You will need to have at least one thrust bearing to keep the shaft stationary along it's axis. Make sure this bearing will handle the thrust from both forward and reverse. You will also need a regular rotational bearing to support the load from tensioning the belt.

All of these parts can be found off the shelf. For simplicity I would mount the electric motor so you can move it to tension the belt instead of using an idler pulley. One less part to worry about.

If you need more advice, please PM me.
________
Depakote Pregnancy


----------



## klem (Oct 16, 2009)

nickmerc is correct about using a belt drive an needing bearings. The only thing that I would add to it is look at the gearing that you want. A lot of the electric motors you will be looking at spin around 4k rpm max which you are going to want to match to your maximum shaft rpm which is closer to 1k-1.5k usually. This will mean having a reduction in your belt drive by putting a bigger pulley on the shaft end.


----------



## arf145 (Jul 25, 2007)

Architeuthis said:


> Few people realize what evil power lies under the hood of the lowly gas powered car. It isn't the internal combustion engine whose power is merely fire contained, it is the starter motor, a direct tap into a fundamental force of nature....


Cracked me up. Thanks Architeuthis.


----------



## COOL (Dec 1, 2009)

Architeuthis said:


> Enter the starter motor.
> 
> (not to mention any hope of getting a girlfriend)


That is a beautiful story.

If you are not already familiar with it,
do a You Tube search for:
'White Zombie' electric car.
Awesome stuff.


----------



## Architeuthis (Mar 3, 2008)

White Zombie is a great car and shows what can be done with electric cars. 

If it was not for the fact that there are no patents left on a basic electric car I'm sure we would be driving them today. The technology is older than cars themselves. 

And the motors can be very powerful. A starter motor from a big block engine can provide kilowatts of power. With only increasing the size of the cables, we even used the orginal starter relay, we got a starter motor to run at 400amps. Peak current was over 600amps (max for our instruments). That's about 4KW from a motor you can hold in your hand. 

Well not after it was running under that load. We shut it down after 15 secs or so as we didn't want to burn anything out and we didn't. That motor went on to serve as a starter motor for many years. 

It just goes to show the kind of power that can be had from a very simple and cheap electric motor. 

Which is not what Kilavolt or White Zombie are using. Thats some expensive stuff they are working with.


----------



## Architeuthis (Mar 3, 2008)

bmacfarquhar said:


> I've considered the trolling motor option but they seem tiny unless you get the Torqueedo and then they seem overpriced... I've seen people stick an e tek motor on an old outboard.
> 
> I was particularly interested in figuring out how to connect an electric motor to the existing prop shaft if anyone had done something like this and might have a photo or drawing of how they did it. I will look into electric car kits.
> 
> Electric trolling motors may work I am still looking for my boat have a short list and will be buying soon but the exact length and displacement are yet to be determined.


Starter motors have a short duty cycle that can be extended with fancy cooling systems, like water jackets and while they will give you power I think they are more a fun project motor than one I would count on away from the harbor.

If you have yet to get the boat then consider ones with a square stern so you can mount trolling motors.

A pretty powerful trolling motor can be had for $400, something with 75ft/lbs. That is more than you can get from the 2HP Honda outboard. Of course you would be interested in the reconditioned ones as well as the used ones and they can be had for a couple hundred bucks.

The advantage of the trolling motors is over all cost. Controls are easy, no cooling problems (the hot part is in the water), rugged and you would use more than one so if one fails you are still going to have some power.

You want the higher voltage units but above 24volts they seem to get expensive for not much gain in thrust. That just means keeping cable runs short and big.

Another advantage is not losing the inboard diesel until you know electric drive is your thing. Trolling motors can do it but there are draw backs, some differences and some great advantages that are not for everybody.

If you are going inboard then go with the belt or chain drive as you will be changing the gearing alot. If you have an adjustable prop (as I do) then you have even more playing round with gearing to do.

Use a saddle bearing to support the shaft, maybe two one on each side of the sprocket and make everything oversized as a motor can really twist da heck outta things.


----------



## P35juniper (Feb 11, 2010)

*Electric motor*

If you can find and old GE ELEC-TRAK garden tractor, it has a 2.5hp motor, 2.5hp continous hp, or about 5hp for 10 minutes or 12hp for 2-3 minutes, they have all the controler you need to have, forward/reverse, slow to start, if you don't do soft start it would rip the shaft out in short order. and the motor runs at about 2000rpm so if you have a A4 that will run up to 3600 and a 2:1 it's close, 
E-TEC motors will work too,


----------



## GaryHLucas (Mar 24, 2008)

P35juniper said:


> If you can find and old GE ELEC-TRAK garden tractor, it has a 2.5hp motor, 2.5hp continous hp, or about 5hp for 10 minutes or 12hp for 2-3 minutes, they have all the controler you need to have, forward/reverse, slow to start, if you don't do soft start it would rip the shaft out in short order. and the motor runs at about 2000rpm so if you have a A4 that will run up to 3600 and a 2:1 it's close,
> E-TEC motors will work too,


My GE Electrac is from 1970. Completely rebuilt with epoxy fiberglass battery boxes. It now has a permanent magnet main motor driven by a Curtis controller. I have a triple charger that charges 3 pairs of 6 volt golf cart batteries. That does a much better job of equalizing the batteries than the old 36 volt charger.

It may yet wind up in the boat!

Gary H. Lucas


----------

