Electric Outboards

[Expat1]

Can someone out there help me? I have an open boat, just over 3 metres in length, 1 and a half metres beam and weighs 74 kilos. According to the builder's specification, it can take a 5 hp short shaft outboard. It happily pushed along with 3 adults on board with a 3 hp Mercury. I'm thinking of putting an electric outboard on it (her) when I'm next in the UK, but the specs of electric outboards that I've seen don't work in hp, but some other power measurement, such as 'Thrust Level: 28 lbs'. How does this equate to hp? Please don't get too technical, I just want to know what 'Thrust Level' I will need to take the 74 kilos plus 3 to 4 adults.
Also, how is the battery technology these days? How many hours boating could I get out of a fully charged battery?
Should I rethink? Perhaps I'm getting too much sun.

 

[Brayman]

Toomuch sun? Yes, come home.

 

[TrueBlue]

I\'m hoping -

- more folk with actual experience will put their points as well, BUT -

I did some research a while ago and satisfied myself that:-

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These electric outboards are principally designed for silent trolling; that is moving very slowly through the water in pursuit of fish, usually on lakes where there is little or no current.
They are not suitable to propel a dinghy at any real speed.
There is always some current on the Thames - so a trolling motor would definitely struggle upstream
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Although I have seen some slippery craft - Canadian style birch canoes - purring along quietly, I've never seen more than two people in such a craft.

Perhaps some figures might put the issue in perspective:-
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3HP is approximately 3Kw (allowing for losses)
3Kw gives a current draw of 250 amps at 12V
Theoretically a 70 amp hour battery would last for 8 minutes before it became 50% discharged.
So that's a no-no
I think a 28lb thrust motor is approx: 1/4HP.
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NOW if you're prepared to stuff your dinghy full of heavy lead acid batteries, then the largest motor may give reasonable performance, but then how are you going to charge the dratted things up??

I dropped the idea; to me there seemed to be too many challenges. I bought a 2Hp Honda 4 stroke outboard instead; light to carry, fairly quiet at slow speeds, no refuelling problems.

Forget electrics; the power storage issue isn't solved yet, and won't be for a long time.....

 

[Channel Ribs]

I like them. I have a 30lb thrust model as an auxilary on my 22ft sailing boat and it works nicely - great for manouvering in marinas and can even struggle against tide for short spells. Nice and easy to transfer to a tender too, with a lightish 35AH gel battery which gives half an hour of full power.

Based on performance my 30lb equates to around 1HP, it draws just over 30A at max.

Electric ones fall down where you want speed and longenvity, if you are using it on a tender for ocassional running about with plenty of time to recharge then they are great. If you want prolonged power that can be refueled in a minute then you will need a small petrol engine.

 

[Dave_Seager]

I use a Minn Kota Endura 30 on an old Dell Quay Dory 11' with an 85 Ah battery. The dory is very heavy (probably waterlogged) but I can still get a top speed of 3 knots. I have never flattened the battery but it has been fine for outings with up to five people for about an hour.

I use it on the River Wey where the current is probably about 1 knot. It is a quiet stretch where we live and I find the silence infinitly preferable to the noise and smoke of a conventional outboard.

I recommend checking prices abroad. I bought my motor on the USA as the price was about half that in the UK. The box was small enough to be checked in as normal luggage on the flight home.

 

[Gumpy]

I have one sitting in my garage.
Bought it with the folding dinghy I had, it powered that fine.
Sold the dingy and bought an inflatable, the electric outboard just didnt have enough grunt to move at more than a snails pace upstream, even last year.
At the boat show this year I was tempted and bought a 2.5hp outboard, I have yet to use it but suspect it will be miles better than the electric one.

Julian

 

[Expat1]

Thank you all for your help. The strong views either way show the importance of 'is it fit for the purpose'? While the boat is at Henley, True Blue's reasonably light 2 hp 4-stroke will do the job; but I had been also thinking that the boat may end up in Goring where I could breeze up through Cleve Lock to cadge a few drinks off Byron, and, from the information Malthouse and Dave Seager have given me, a thrust 30 electric would do the trick for that job, but, as stated, the batteries are heavy, and would the whole lot end up in the garage, like Parglena's? Maybe I should forget that part and buy my own drinks from Threshers.
Anyway, many thanks to you all. I've learnt a lot and will probably go for the Honda.
Lastly, Ian, the temperature here yesterday was upper 30s (around 100 pre-decimal) and the sun was shining. And the day before. And the day before that. Etc, etc. I'll be back for long enough to stay out of Mr Brown's clutches!

 

[TrueBlue]

General: This thread

I'm so glad you have been able to extract different points of view from all the replies. For once the posts have been clear and have given some terms of reference - so that you could weight the circumstances or the responder's comments.

I've come back to add this postscript in the expectation that others may read the thread before asking the same basic question again.

I have found these YBW fora very helpful in getting information on all sorts of topics including those I wasn't looking for!

The issue for me is that these electric outboards are best suited for trolling on lakes (sorry - I've said that before) and that is how they are sold in the US (where they probably originated). Over here where advertisers don't seem to have a duty of care in what they say, the keyword is "outboard" which in practical terms means something completely different, and becomes a trap for the unwary.

If you are only going to use the boat on "tax exempt" visits, might I suggest you consider a well used Seagull. They are cheap, £75 -£150 on eBay; very noisy, emit clouds of smoke - but that's usually behind you. most importantly they are ultra reliable and being in the best British agricultural style of engineering go on for ever and ever, Amen. I have several and they give me tremendous fun because they are so idiosyncratic...

Thanks for your feedback. Most heartening

 

[whisper]

I've just been watching loads of happy folk passing by in dinghies powered by electric outboards. These are all hire boats on the Avon at Stratford. I believe that these power packs are specifically intended for that commercial use and they seem to perform very well managing about 3 kts upstream. This is in a Linder 4metre boat weighing in at about 105kg plus up to 5 or 6 passengers. Can't remember the brand but they are not in the "Minnecota?" style but are more basic and heavyweight.
Personally decided against buying one due to the carting about of the heavy battery and motor when only using the dinghy sporadically. As others have said, the lighter type are essentially trolling motors for fishermen and are often an auxilliary for a petrol engined outboard boat.