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MetroMPG 07-01-2009 02:36 PM

Fun weekend project: solar assisted electric boat conversion
I spent the weekend and beginning of this week at a cottage, and had some play time messing around with boats & stuff:

  • solar panel is a Sharp 80 watt scratch & dent special that I got used on eBay, lashed to the deck of a...
  • Laser sailboat hull
  • 12v battery is the old one from the Blackfly
  • electric motor is a used 17 lbs max thrust Minn Kota trolling motor - yard sale find
  • instrumentation: digital multimeter to monitor battery voltage
(Yes, this is where to insert peanut gallery comments questioning the wisdom of converting a sailboat to a powerboat, even if it's an electric one. I can promise that when the wind was blowing, the mast & sail were on the Laser and it was being used properly!)

This is sort of an evolution of the Forkenoe electric canoe project from 2 summers ago:

MetroMPG 07-01-2009 03:20 PM

Well, the title of the thread isn't quite right.

It was a solar powered boat - not just solar "assisted". All the power used came from the sun.

But the 80 watt panel wasn't powerful enough to run the motor in "charge sustaining" mode, because its minimum draw on low was about 116 watts.

So I guess that makes it a "solar range extended electric boat"? And the deficit was made up while it was tied to the dock and the battery was recharging.

MetroMPG 07-01-2009 03:30 PM

dcb 07-01-2009 03:50 PM

what is the relationship between speed setting and actual speed?

Tango Charlie 07-02-2009 09:42 AM

The ice has melted off the lakes already?! :p

MetroMPG 07-02-2009 02:18 PM

Oh hush.

Though I dove into the St Lawrence yesterday afternoon (Canada Day!) and it nearly took my breath away: 65 F / 18 C. I thought it was closer to 70, but I was wrong :)

Dave, I'm not sure what speeds it would do on the different settings - no GPS. Last time, on the canoe, I figured the top speed setting was good for about 8 km/h / 5 mph, in no wind, flat water.

Tango Charlie 07-02-2009 03:28 PM


Originally Posted by MetroMPG (Post 113440)
...I dove into the St Lawrence yesterday afternoon (Canada Day!) and it nearly took my breath away: 65 F ....

I always wondered what was the proper way to celebrate Canada Day. Now I know. Ha ha! :D

tasdrouille 07-02-2009 11:47 PM


Originally Posted by Tango Charlie (Post 113447)
I always wondered what was the proper way to celebrate Canada Day. Now I know. Ha ha! :D

Yeah, we're lucky it's July 1st! 2 weeks earlier and the ice wouldn't have sunk yet :P

Joking aside, Darin, any plan to play with propeller design? The stock "gearing" is not optimal for such a light boat.

orange4boy 07-06-2009 12:19 AM

Love it... LOVE IT!

It's never a dull moment with you on this forum MetroMPG!

I did something like this a couple years ago... I needed to get my Tornado catamaran in from the buoy to the launch ramp sans sail. About a one mile trip. I don't have an outboard so I got to thinking about my 12V dewalt cordless drill... Hmmm 12V car battery, 1/2 inch chuck... 1/2" stainless rod kicking around. I welded up a prop with some scrap stainless sheet, added a ball bearing so I could hold on to the shaft while it spun and Voila! instant portable aqua thrust. I dropped a car battery into my kayak with wires to my dewalt held the bearing in one hand and the drill in the other and drove myself to the cat. Transferred the battery to the cat and powered her in.

I passed a couple on a skiff, paddling out to their boat.

Them, (incredulously) "Is that a cordless drill?"
Me, "yup"
Them " (laughter) Cool."
Me," I'll see you when the oil runs out."

I've been looking for a cheap trolling motor ever since...

MetroMPG 09-22-2009 04:57 PM

Delayed response...


any plan to play with propeller design? The stock "gearing" is not optimal for such a light boat.
No plans yet. I don't know much about propellers, other than there are different pitches available for the motor. I've always thought the prop had a very "shallow" pitch - ie. it spins a lot relative to its motion through the water.

ORANGE! You have a Tornado? Fun boat! I've got a really beat up Hobie 16 that hasn't been in the water for 2 summers. Oh, and a Proa that I got for $20 and used a couple of times :P

Your "get it to the ramp" story reminded me of this:

Hugh.H 12-13-2009 07:20 AM

Ah, this was the thread I was hoping to find. I picked up a used 24' powerboat and I have a question. I apologize if it is completely clueless but I'm about to get on a flight and I wanted to ask something before I spent the better part of a day getting to the other side of the planet. I'm easily distracted so I wanted to ask before I forgot.

We also managed to snag an unused new-in-box 82lb thrust, 24v, saltwater, variable speed PWM wireless Motorguide electric boat motor.

I realize that the hull drag from a 24' boat will not break any speed records ... but it was more of an emergency backup means of movement should the main engine fail. Since we are on the Gulf of Mexico (and assorted back bays) an engine failure could be a life threatening (or ending) event. It would be nice if we could somehow limp back to shore or the boat ramp given enough time, favorable winds/currents/etc.

We also have a LOT of solar cells of various types and were looking to custom build a charging system using the front of the boat (not going to get into that here, but since the boat would be in the sun more often than not it would add something back over time)

Which brings me to my question. We were looking at various means of storage and I came across the LifeYPO4 batteries as listed on Assuming for a brief educational hypothetical moment that we had the funds to get the largest of what they had (see link below for specs), and assuming we could fit 8 of them in the boat in series for 24v ... would the cruising range be worthwhile doing running at the lower end of the power spectrum? With the hull drag I am more interested in being able to move as far as possible - it doesn't have to be fast.

Based on the specs below and the motor requirements, how many kWh is that anyway? 19200?

or the short version:

Nominal Capacity: 800Ah
Operating Voltage:2.5V - 4.25V
Weight:26kg 300g
Dimensions:850 x 288 x 71(mm)

I'm sure there is a whole slew of charging considerations that need to be factored in as well but first I'm curious to know if it would be pointless to go this route at all.

This project already has a lot of the big components. The boat is in excellent shape. The motor is in excellent shape and still under warranty. I have enough solar cells to fashion any sort of charging setup and could cover every available square inch of exposed surface and encapsulate them if it was practical. (specs on what cells I have can be discussed later, I'm more curious about the potential range of these batteries)

If anyone could share some thoughts, ideas, or comments that would be great. I don't know what the max amp draw on the motor though I did read somewhere someone had mentioned 40amps on theirs but I don't remember the details of their motor specs. I won't know more until I get back to where the motor is but maybe someone will have a rough idea.

Thanks for reading through this. I won't be able to reply for a day or two. My flight leaves in few hours.


MetroMPG 12-13-2009 02:41 PM

Hi Hugh -

82 lbs thrust on a 24 foot boat...

Because you described this as potentially a "life or death" backup, I'd play it conservative and say: not worth the risk! Find a smaller internal combustion outboard instead and bolt it to the transom. Even the smallest you'll typically find is probably going to have more power & useful range than that e-motor. A used one will cost a lot less than a lithium pack, too.

The playing around I did with the electric boat was just that: playing around. On water flat as glass. Any chop or breeze whatsoever, and my (obviously much lower powerful) motor would have been uselesss. But then I could have sailed. :)

Hope that's not too discouraging a response.


Hugh.H 12-31-2009 11:33 AM


Originally Posted by MetroMPG (Post 147225)
Hi Hugh -

Hope that's not too discouraging a response.


Thanks for the response :)

Just after Christmas we moved the boat to our local area and it is now in the driveway. Even though it is likely that this project won't pan out we already have the materials so I might as well give it a shot and see how it works out.

I started taking measurements of the available (and viable) surface areas for potential cell placement. I'll post pictures of the boat later along with some of the cell types that we have available.

At this point I'm not overly concerned with massive amounts of storage due to the expense and/or weight. We'll put the motor in a barrel and hook it up to some panels to get a rough idea of what (if anything) can be realistically used by the motor. That will be a lot cheaper than modding the boat only to find out that it's not going to work :thumbup:

two additional ideas are to layer the polycrystalline cells with an organic dye overlay to try and make better use of more of the light spectrum. It may not be possible or the additional weight may be prohibitive. Anyway, it is just an idea.

The other idea is to eventually fabricate the panels so that they can be raised and used as stiff/solid sail. Obviously there are some interesting possibilities and a lot of problems but a hybrid system (of sorts) could be useful.

Someone asked me "why do that with a powerboat?" ... and to be honest there aren't a lot of good reasons especially since there are other marine platforms better suited to such endeavors. But we have the parts so we are going to go ahead and give it a try and maybe someone else can make use of the information/results.

I'll post pictures of the boat, motor, and other materials later. Thanks again for taking the time to write back. I appreciate it! Happy New Year!


Hugh.H 05-16-2011 02:58 AM

Well ... fast forward 18 months. Decided that my interests were a little on the expensive side and decided to stay abroad a while longer doing overseas work to help the piggy bank out.

I came across something that has some interesting hacking possibilities. it seems that someone has fitted a battery operated hydro-jet module to surfboards to help surfers get through the breakers. Very sleek. www . wavejet . com (sorry for the spread-out link. I'm not allowed to post URLs yet)

Popular Mechanics happened to mention it as well.

20lbs of thrust for 39 minutes in a 17lb modular package. No additional specs are available that I could find ... but it does raise some interesting possibilities that might be worth mimicking in some form or fashion.

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