make an electric trolling motor into an inboard?

[TomF]

The search function pulls up several threads on electric auxiliary power - for small boats, the consensus seems to be that a Minnekota trolling motor is an efficient, cost-effective choice... but I hate the look of outboards on traditional sailing boats that never had them.

I (still) fantasize about building a 17 foot sprit-ketch Hampton boat. Feedback from 'round here is that those designs would benefit from some internal ballast, since I'll not be loading it down with a day's catch of cod!. A few well distributed batteries might be just the ticket.

Hamptons were also reputedly very easily driven by low HP auxiliary inboard engines.

So, has anybody done the obvious, and found a way to cut up a bassboat trolling motor, and use it to drive a traditional deadwood-mounted propellor shaft? Or would I be better off to explore other electric options, like electric golf cart engines? Don't know how big those are.

My auxiliary use would be primarily for when supplementing sail if it's necessary to get home on-time while fighting the 3-4MPH current in the river where I'll be doing most of my sailing.

And yes, I'll also have oars.

Tom.

[Mike Vogdes]

I have seen people build a trolling motor into their rudder but a 3-4MPH current is pretty strong for a trolling motor.

[ssor]

There has been considerable discussion on this subject in a current post. Look for motor in a piccolo canoe

[TomF]

Thanks - I'd missed that thread, not being interested currently in building canoes...

Yes, looks like I might need to consider a heftier power plant for my heftier proposed boat.

t.

[shadow99]

There's a great article here

http://www.stevproj.com/EMotorIdeas.html

Such info as what style batteries, photos of the construction of his particular method of aux. power. Pretty good stuff, I used some his ideas on my own vessel.

Rick

[RonW]

As to your remarks - (hamptons are very easily driven by a low horsepower auxillary inboard)
opens up a whole new disscussion.

Once you get past the trolling motor idea, and get to the point where you have a shaft turning a fair size propeller things change.
A boat of this size and weight would (guessing) probably need at least a 16 or 18 inch prop and a 5 horse motor.Minimum to be realisitic.
And that probably means at least a 24 volt system or more like a 36 volt and possibly as much as a 48 volt system. Remember amps times volts = watts. On a 36 volt system you would need 6 golf cart batteries, and that limits your running time to the amperage of the battery.Again guessing maybe 2 or 3 hours at most. To double this time you need to double the volume of your batteries or go from 6 to 12 batteries.
Weight and room start adding up.

To put a system like this on a sailboat, that was just a backup power source that you probaly would not use for more then a hour or so each time out is very do able.

On the other side of the coin to build a launch of reasonable size and use elctric, in comparison to a small diesel with 20 or 30 gals fuel, the diesel will run 3 or 4 times as long and go 4 or 5 times farther with 1/3 the weight and room.Generally the diesel will run the launch at higher speeds. But just for a kick on and off sytem on a sailboat of reasonable size might be quite doable and interesting.Read this.--
Also look up duffy electric boats.

http://www.electricboats.co.uk/intro.html

[ssor]

I once read the a gallon of gasoline has as much potential energy as a ton of lead acid batteries.
If you are not too concerned about reverse then a small air cooled gasoline engine with a centrifigal clutch and a vee belt reduction drive will take you a long ways for not much cash.

[RonW]

In being realistic, I think a gallon of gas is approx. equivalent to about 200 lbs. of lead acid battery, at 30 times the weight and 3 times the volume. Just a little lop sided.

[Steve Miller]

Look at the 20' Secret by Scruffie Marine. They have done just what you are thinking it seems.

Scruffie Marine (http://www.scruffie.com/)

[Frank Wentzel]

But you can't recharge a gallon of gasoline! Then there is noise, reliability and safety. Not that electric propulsion is the answer to a maiden's prayer but the equation is not totally lopsided.

/// Frank ///

[ 02-11-2005, 07:18 PM: Message edited by: Frank Wentzel ]

[Geoff C]

Devlin has a design (Nancy's China DC) with a trolling motor built into the rudder. If you are using it as an assist to the sails, it should be sufficient for a 4 knot current. As a bonus, the batteries should add a little ballast but should be kept from being flooded by bilge water for obvious reasons.
http://www.devlinboat.com/nancyschinadc.gif

[ssor]

Ron, you are quite right. I just compared the fuel consumption rate of a Honda generator to the out put of a battery. 6 Group 31 batteries will yield about the same volt-ampere total as one gallon of gasoline. Of course I prefer the silence of sails to the racket of an engine. redface.gif

[ssor]

On the electric propulsion idea, would a Vetus bow thruster serve? they come in many sizes are nicely packaged and well known.

[Chris Gerkin]

I built a Stevenson Vacationer and built in a 44 lb trolling motor. The boat was to be used in a lake. If I were doing it over I would have used the biggest trolling motor I could find. I subsequently moved to the ocean and switched to a 7.5 mercury in a well. Here are pictures of the trolling motor setup. It was simple.

http://www.imagestation.com/picture/sraid40/p733338e6e9bd5b838f639f53e1456dce/fcffde45.jpg

[RonW]

http://www.glen-l.com/designs/special/electricdrive.html

Here is glen-l's ed, a lower unit off of a outboard, mounted with a electric motor inside running the shaft by pulleys. Pretty neat, you could get much bigger props that way.You can also link over to one of their electric boats and pick up some info.
I am under the opinion a bow thruster is nothing more then a over priced trolling motor in a tube.

Think Chris made a good point that trolling motors and their small props just do not have the oomph needed on larger boats and rougher conditions, a bass boat only weighs 1200 lbs without motor, and they are now setting them up with 100 plus pounds of thrust and 24 and even 36 volt trolling motors.

I still say that I think the ideal and usefull setup would be to replace a small 5 to 15 horse auxillary diesel in a sailboat that is used for day sailing or weekends with a electric.
You would have to have a shaft,so you could use a large prop and be willing to limit it's use to from 3 to 6 hours max. and lower speed of like 5 or 6 miles a hour.With a reastat control you could idle it to nothing, saving a lot of battery and making the boat real manueverable.
With in the limits, it would take no more room or weigh no more then a small diesel, battery's and motor, have a lower profile, probably cheaper,
and you wouldn't need a cooling system, or exhaust system. No fumes or noise.

There where some electric boats built right at 1900. that ran 50 m.p.h. but that was only for a few minutes at a time.Our battery technology is too far behind to make it pratical, compared to a gallon of gas. But as a aux. kicker on a day sailer with a shaft, might be interesting.

[AngWood]

Also look for threads about John Blazy's Calypsee. I think one is called "Primary Electric Propulsion," maybe in Building/Repair. He's got a website at http://www.pbase.com/dr_dichro/electric_boat

It sounds like you're thinking of mounting the motor itself on the inside of the hull, but I believe trolling motors are meant to run submerged, which keeps them cool. Plus it's easier to chop the trolling motor shaft short and mount it in a tiny well (even a tube will do).

[RonW]

Not trolling motors, but real motors connected to the shaft, with a real prop,(large).

http://www.electricboats.co.uk/jpgs/VetusElectricPropulsion.jpg

[ 02-14-2005, 07:56 PM: Message edited by: RonW ]

[Dan McCosh]

FWIW, GM's EV1 electric car had about 800 lbs. of batteries, and a range of about 80 miles with lead-acid batteries. The same car would obtain about the same performance with a gas engine that could achieve 70 mpg. This would indicate that about 700 lbs. of batteries are the equivalent of about one gallon of gasoline. The demands on a marine system, which is a constant demand on energy, would be tougher on the battery, however, while electric drive at low rpm is a bit more energy efficient than a geared-down IC powerplant. The interesting concept for a sailboat is if you could use the batteries as a substitute for a lead keel.

[TomF]

The Vetus looks grand ... until you see the $5K plus pricetag.

I'm back at the idea of purchasing components from electric golf carts - perhaps one of the motor designs which are scoped to provide additional torque at low speeds - and make up a system from that.

Won't be cheap, but will be much cheaper than off-the-shelf Vetus. Of course, you get what you pay for! They've done all the design work for you ...

Tom.

[nedL]

Golf carts work. ---More than 20 yrs ago I worked in a shipyard where (as a side line) we built reproduction launches (gas, steam, or electric power). I did a lot of the building of them & all of the power plant installations. For the electric ones I'd go up to a golf cart repair place and buy a used electric golf cart ($100 as I remember) and have it sent to the shipyard where I'd strip all the electric drive out of it & install it in the launch with a flat timing belt drive to the prop sahft. A bit more involved than just that, but they worked out pretty well.

http://www.imagestation.com/picture/sraid11/p815d3a8877f072cbdc5f9705fbe48fa2/fe12645c.jpg
"Golf cart" powered launch.

[ion barnes]

nedL - Did you use the timing belt for gear reduction or just as a coupling?

[RonW]

Well alright, it seems as if some of us are on the same page.Here is a very informative page of the beckman steam and electric launch co. out of Rhode Island.They sell a complete system for about $4k, batteries not included.They install these on 30 foot launches and sailboats.

http://www.steamboating.net/page40.html

I think if you knew what you where doing, you could piece together a system for about half that price, but their system does look first class.
Their motor also runs in reverse which is very nice, and I think golf cart motors use a transmission.Golf cart motors run from 1 to 10 horse and sell for $500. to $1000. roughly.
My research says that a one horse electric motor is equivalent to about a 8 horse gas. This is because the way the motors are rated, a gas is rated at peak performance where a electric is rated at constant power. So a 2 horse electric will replace a small 15 or 16 horse gas engine.

Batteries- with a 2 horse elec.motor and approx. 750 lbs of batteries,or 12 -12 volt batteries at 130 amps, that is enough power to run a 4,000 lb boat at approx. 7 m.p.h. for 10 hours and at 4 m.p.h. for approx. 40 hours, enough auxillary power for a sailboat for a whole week, more then enough, you could even down size the system.
That equates to about 70 miles on high and 160 miles on medium.Even on a launch and using this as your only power source you wouldn't use it up in a weekend of playing around.

The major part of this system is using a regular shaft and large prop instead of little trolling motor props.In comparison about a year ago I checked on a westerburke 10 horse diesel, that came with the gear box, no shaft, (although you felt the shaft) at $4,500..

The beckman system includes the items needed to plug into shore power and these sytems only take 6 to 8 hours to fully recharge.
The duffy electric boat site I mentioned above has changed and they dropped their big boat.
It was very impressive I thought, It was a 30 ft. custom cabin launch, that ran on a 48 volt system with a top speed of almost 10 m.p.h. and a total running time of almost 100 hours.It had solar panels on the roof and a onboard generator plus being able to be reacharged in 10 hours I think by shore power.But probably cost over a 1/4 mill.

Bottom line is elctric is very doable as a aux. power source in sail, and as primary power in a launch. Maybe Nedl can tell us more about buying used golf carts with all the parts included.

[nedL]

Ion Barnes - The timing belt was for reduction also.
Ron - What would you like to know? The golf carts that we used did not have transmissions, the motors were direct reversing which made reverse in the boats real easy. I went up to Providence R.I. for the golf carts, picked out 3-4 that looked OK mechanically and had them delivered to the shipyard in southern R.I.

http://www.imagestation.com/picture/sraid11/p6bd64e5b408e4cd7ed9cfe0251f0baca/fe126408.jpg
Her's another picture of the same electric launch.

[ion barnes]

OK Ned, tell us more. Describe the design. In-line, piggyback? size of prop, reduction, flat belt, Vee belt, cog belt, etc

[RonW]

I agree with ION. get down with some hard core info, what was the ideal prop speed,( mid teens?).

I guess everything you need is right there on the golf cart, controls and even a voltage transformer to plug it in to regular electric source for recharging. Add a few fancy gauges.

Looks like the price of used golf carts may go up.They have built a lot of golf courses around the country in the last 30 years, so getting a cart should be no problem.