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Old 03 October 2014, 16:07   #1
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3.1m SIB + elec motor

I have a 3.1 Zodiac (air floor) and am thinking of an electric outboard for the canals (I have a 6hp Evin. for the sea) I am looking at a 44lb thrust with a 60ah battery. Does anyone have an idea of how long this would run for 3 up. Obviously it will be a guestimate. I hope it will be about 4 hours or so. (4mph max remember on canals and I don't expect it to go much faster).

Thanks all

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Old 03 October 2014, 18:52   #2
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There is a formula to work it out and it was explained to me a few years ago but I cannot remember how to do it. I would use a 120 ah leisure battery if I were you. I have a 32lb thrust motor running on a 120 ah but have never tested it for maximum running time.

Phil
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Old 04 October 2014, 04:57   #3
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Some very good info below if your brain does not go into meltdown


how many lbs of thrust is equal to 1 hp? - Boat Design Forums

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Old 04 October 2014, 05:13   #4
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Quote:
Originally Posted by apshutt View Post
I have a 3.1 Zodiac (air floor) and am thinking of an electric outboard for the canals (I have a 6hp Evin. for the sea) I am looking at a 44lb thrust with a 60ah battery. Does anyone have an idea of how long this would run for 3 up. Obviously it will be a guestimate. I hope it will be about 4 hours or so. (4mph max remember on canals and I don't expect it to go much faster).

Thanks all

I haven't done the maths but can't see it being likely you'll get 4hrs with a 60ah battery. there was an article in a recent pbo that I picked up whilst in a train station that might be of interest.
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Old 04 October 2014, 05:27   #5
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So back of fag packet that page says you use about 40amps each hour. You'd KILL that battery in 90minutes, but you should expect to be getting to about 40% of the 60amps and then needing to recharge or you kill battery for good... So under an hour of use. I'd want 2x 120ah for 4hours use.

These electric motors are really of most use to fishermen on lakes.... 10minute motor out and anchor / drift. 10 minutes motor in. Similar use for yacht tenders..
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Old 04 October 2014, 05:48   #6
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Another link below a bit more user friendly just scroll down to the 'battery power and thrust' chart

ENGINES

It looks like it is 52 amps
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Old 04 October 2014, 09:09   #7
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That is a useful guide Bartiny.
If electric power is what you want, firstly sit down and then look at Torqeedo outboards. I had the Ultra Light on my kayak but you will be looking at approx 1300. The efficiency of these motors is amazing but you really have to read the data to see where your money goes. The price is high but the technology put into these motors is something else. I will actually be testing the 3hp when my good friend from Torqeedo comes up north next. Just to give you an idea of weight, my Ultra Light motor + battery + hand controller with full data readout = 15 lbs all in.
Phil
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Old 04 October 2014, 17:03   #8
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Thank you all for your replies, very useful. I have scrapped that idea now. 2 x120ah batteries is just too much weight, I thought an elec motor with battery would have been a quiet and easy (Lighter) option than lugging the Evin 6hp about and petrol tank for going up and down the canal (my wifes pleasure). Although the elec will be quieter the thought of carrying those batteries gives me back pain, and that is my trade!!
link removed

Thanks once again guys, I might just invest in a smaller 2 stoke

Blessings to you all.
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Old 24 October 2014, 10:29   #9
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If you win the lottery then get a Torqeedo 1003S equivalent to 3HP outboard). Self contained battery, GPS rangefinder etc. Pricey but worth it. I have a 5HP outboard for inshore and use the electric motor for inland lakes, lochs etc.
Can do 16 miles on low throttle (up to 8 hours) and resolves the problem of an emergency alternative when inshore as its only lightweight.
As this is a "true" electric motor it will return the same power as a 3hp petrol outboard unlike the "thrust" type that return 0.5HP if you are lucky. It will drive up to 1.5 tons.
The downside at the moment is it is expensive but it really is first class.
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Old 24 October 2014, 14:21   #10
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For canals, a tiny petrol outboard will be light and perfectly adequate - just a couple of HP.

Maybe go all retro and pick up an old Seagull and some ear defenders.
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