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Old 22-04-2010, 18:03   #1
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Electric Dinghy - Real Experiences ?

I've been seriously thinking about purchasing a 9' Fatty Knees hard dinghy (Edey and Duff: Fatty Knees, Videos).

By my measurements it will *just* fit on deck for passages or if things get squirrelly, but I expect that I'll generally be towing. I really love rowing and will actually be able to use this to zip around our local marina and surrounds in the evenings, which would be great. However, I've read enough (and been flamed enough!) in other forums to know that sometimes an outboard is most definitely your friend.

But, I'd like to keep it light and minimal if I can. I've been toying with picking up a Minn Kota saltwater trolling motor (Riptide Transom | Saltwater Transom-Mount | Trolling Motors | Products | Minn Kota Motors).

Does anyone have any experience with a similar motor with a dinghy? Specifically:

(1) How far / long can one travel on a charge?

(2) Recommendations as to thrust level (options seem to be between 45 and 101)?

(3) What have you found is the best way to manage the battery/ies and charging? Any specific recommendations or tips?


Please don't blast me with the 1,001 reasons why diesel motors are "superior" - I've read enough to know all the usual arguments. I'm really just wondering if anyone has some real world experience and data from a similar set-up they wouldn't mind sharing?

Thanks in advance!
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Old 22-04-2010, 18:45   #2
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Personally I'd never recommend a diesel outboard. A lot of dollars for the performance you get. I have had three clients that insisted on buying the Torqeedo electric motors with spare snap on batteries for their dingy. I beleive their performance is better than most trolling motors. That being said, all three returned them in favor of small four strokes. If it's the quiet your after in nice calm achorages and marinas I say why not a Mini. But when in areas with stronger currents nothing beats fosil fuel.
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Old 22-04-2010, 19:13   #3
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How far you travel on a charge depends much more on the battery than the motor. To illustrate the point, you would travel a few feet on a flashlight battery. With a giant golf cart battery you would go a few miles.

So it comes down to balancing how large a battery you can safely carry in the dinghy. Of course the larger the battery the longer you can motor but you are giving up the load capacity of the dinghy.
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Old 22-04-2010, 20:28   #4
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Hi, we have an 8' Porta-Bote and and minne kota electric 28lb motor. We put a 12 volt battery under the seat, in a battery box, and it runs us around the marina and to shore with no noise at all. It will run us over to the club when we don't want to drive around the point. I have run it for hours and never lost power. I would not want to rely on it in heavier weather though. For that we have just gotten a little 2 stroke 2hp outboard. We sail with the pooch and trips to shore are a necessity when on the hook. Cara will go in the cockpit in desperation, but it does not make for a happy puppy girl....
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Old 22-04-2010, 21:55   #5
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I did the Minn Kota type thing for my 12'8" plywood epoxy sailing dinghy. Overall, I'd say it was not a good solution. I have huge issues trying to put a gas outboard on my sailing dinghy due to weight and hull design. So I tried the electric. Admittedly, I used a small 12v battery so the range wasn't great but I had two and figured a small one would be easier/quicker to re-charge. Well, that has been less than satisfactory. I had one occasion to motor-row against a left over chop and head wind when I'd rather have just twisted the gas throttle up a bit higher.

For me, the uncertainty of having adequate juice OR time to recharge means I'm never really able to rely on it.

Bottom line, I want a sailing dinghy that can easily handle a 2hp 4 stroke, maybe even in a well. Currently, I have three dinghies and am 'under orders' for no more. There's much truth to the total convenience of a RIB with decent outboard. However, beyond pickup duty and taxi it lacks much.
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Old 22-04-2010, 22:45   #6
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Big weight differnence between my little 8' folding that weighs in empty at 60lbs, and a plywood dingy! I can imagine that a little minn kota would not be up to the job at all!

that 2 hp sounds good to me... if it has sailing rig it will weigh even more so maybe 3hp?
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Old 22-04-2010, 23:33   #7
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Aloha,
I've plenty of experience with the MinnKotas and you'll find all the postings if you use the search engine after my signature and type in electric outboard. The club has had three and each has failed within 5 years of abuse but one was able to be repaired. They did not take a dunking and keep working. Ours were from 27lb to 45lb thrust the larger was the saltwater version and has held up best and has quite a bit more power. It powers our 19 foot West Wight Potter with no problems at all if the larger 12v battery is topped off. It will not go against a headwind and chop but gets us to the mooring when the wind dies.
The topped off battery is key to their efficiency and performance. I used to have a heavy 12ft fiberglass dinghy and used my 27lb thrust on it for four hours one day in calm water at half speed with a topped off heavy duty RV battery.
Hope this helps. I'd get a used one on eBay and experiment before buying a big brand new unit.
regards,
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Old 02-12-2012, 13:33   #8
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Re: Electric Dinghy - Real Experiences ?

Real world; see photo's of our large dinghy. I have a 92 AH AGM battery with a cheap little solar controler attached to a 75 watt solar panel. Same set up would be successful with a MUCH smaller solar panel, but I bought it used and made it work. Had a custom made bracket made for the panel. Cost and weight of this system vs. gas was similar. We never charge this battery on land. MinnKota 12 volt 55lb thrust motor. The system is silent and 100% solar powered. Our longest dinghy trip was 3 hours. Max speed with an inflatable bottom is a touch over 3.5kts. I'm not sure how much better the performance would be with an RIB or hard dinghy...but I assume batter. We have had 5 people (2 adults and 3 teens) on board when a storm blew in while in Chicago and we had to make it about a mile back to the boat in heavy chop and head winds. Would a 10 HP outboard have been better in that situation? Yes. Did we make it back safely in good time? Yes. If I could have more power without adding the weight of a second battery that would be great. Lithium prices are still hard to justify. But in time that will adjust and the electric dighy will become common.
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Old 02-12-2012, 13:54   #9
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Re: Electric Dinghy - Real Experiences ?

Nice to see this thread revived after two years. I'm in the process of setting up both an electric dinghy and kayak. For a test run the kayak did 7 miles on 288 w-hr. Tuesday UPS will be delivering my Winston lithium cells totaling 2560 w-hr, so range should be around 60+ nm. For the dinghy I'm going with the Takacat Lite, catamaran bottom air entrapment hull that planes with just a 3 hp gas outboard. Will probably use the Torqeedo Cruise 4.0 with high speed prop.





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Old 02-12-2012, 14:58   #10
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Re: Electric Dinghy - Real Experiences ?

I have the 55 lbs. short shaft riptide salt water, right now with the standard prop. It works great for what we use it for, which is back and forth short range to the beach. I have a little agm battery that I charge off the inverter on the big boat. It's enough to get two adults and an eight year old kid around. The battery is one that I already had, although I'd like a bigger one.

This spring I'm planning on upgrading to a Kipawa prop, which folks on the electric_boats list have all had good luck with.

Depending on your usage pattern, it may be great (like it is for us) or a huge disappointment (if you regularly travel long distances via dink). Luckily, at $250 retail, it's not a terribly expensive experiment.

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Old 02-12-2012, 15:24   #11
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Quote:
Originally Posted by deckofficer
Winston lithium cells totaling 2560 w-hr, so range should be around 60+ nm.
This sounds cool...can we get the weight and cost of this battery system?
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Old 02-12-2012, 15:33   #12
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Re: Electric Dinghy - Real Experiences ?

I do my batteries for the kayak as (2) 12 volt units. (4) 3.2 volt 100 a-hr cells banded together. That way, no matter how carried away I get in distance from the mother ship, I always have the 2nd battery to drop in the battery well. Each 12 volt pack has the physical dimensions of a group 24 battery and weighs 31 lbs. Total cost for the (8) cells is $880.

If you know your use will be less than 30 miles just leave the 2nd battery behind.
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Old 02-12-2012, 21:00   #13
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Re: Electric Dinghy - Real Experiences ?

Wow, $880 is a lot of gas in my 2.5HP Eninrude (like probably a lifetime supply)! But the instant on of electric IS nice.
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Old 02-12-2012, 21:16   #14
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Re: Electric Dinghy - Real Experiences ?

I hope to refit my next boat with an all electric galley and plan on not having propane or gasoline onboard.

Granted $880 is some coin, but with the cycle life they will outlast me. 150,000 nm lifetime without the smell or noise of a gas engine is sweet. At 1/2 cent per mile it is cheaper than gas in the long run.
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Old 03-12-2012, 14:50   #15
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I hope to refit my next boat with an all electric galley and plan on not having propane or gasoline onboard.

Granted $880 is some coin, but with the cycle life they will outlast me. 150,000 nm lifetime without the smell or noise of a gas engine is sweet. At 1/2 cent per mile it is cheaper than gas in the long run.
Good points for sure. I look forward to reading about how it goes!
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