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Electric outboard on 18/19ft cruisers? Anyone have any tips?


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The boat (Shetland) weighs about 600kg plus about 200kg of stuff on it and usually just me. It's on a narrow canal and will only putter up and down on a short range this year. A 5hp outboard has been more than plenty in the past for a similar boat. My questions are

 

Would a 48lb thrust electric outboard push it along and stop it okay? If not, what would it really need?

What kind of range could I get out of an 85Ah battery without trashing it? Recharging would have to be done at home so I don't want bigger.

 

Reason for asking is that I recently got another little sailing boat and it came with a 48lb thrust electric (it had been on a lake). But it's no use for where I sail which is tidal river and needs at least  5hp working flat out at times for a similar weight boat. If the electric will be okay on the boat on the canal I'll keep it. If not, not sure!

 

Many thanks to you wise folks for any advice.

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A good question! Why is it that electric outboards are rated by thrust when petrol ones have horsepower? Is it a deliberate attempt to frustrate comparison? And am I cynical in thinking that the electric motor manufacturers have done this because their products don't come well out of such a comparison?

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Less power than a small Seagull probably wouldn't be great marketing. They always struck me as great for the lake fishing fraternity but I know nothing about them. I do suspect that one won't get the Shetland's planing hull up on the water!

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He's no idea what he's talking about on the technical side, but he's running a 68lb thrust trolling motor on an 18' cruiser.

 

 

 

Edited by TheBiscuits
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Was interesting to see that. That was a Microplus so similar to the Shetland and he could get it fair batting along with 68lb.  Seems to suggest that 48lb would be okay for aimless pootling up and down.

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Just now, BilgePump said:

Was interesting to see that. That was a Microplus so similar to the Shetland and he could get it fair batting along with 68lb.  Seems to suggest that 48lb would be okay for aimless pootling up and down.

 

I'd say fit it and try it.

 

You already own it, and if it works you are laughing.  I think I'd leave the outboard attached while taking it for it's first spin though. :D

 

The fishists usually reckon on getting about an hour of thrust on one 110Ah battery on the 55lb motors.  Treat batteries like gas bottles, and have the spare one not connected until the first one runs flat so you can get back, also try and head upstream/upwind on the way out so you are more likely to get back ... 

 

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23 minutes ago, TheBiscuits said:

 

He's no idea what he's talking about on the technical side, but he's running a 68lb thrust trolling motor on an 18' cruiser.

 

 

 

This one's a bit more coherent.

 

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Yep after that video realised how easy it would be to throw a few hundred at batteries but the other thing I'd completely forgotten about - electric discount - 25% - so about £140 saving on a licence for 18' er.

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1 hour ago, BilgePump said:

Yep after that video realised how easy it would be to throw a few hundred at batteries but the other thing I'd completely forgotten about - electric discount - 25% - so about £140 saving on a licence for 18' er.

When you have spent 1000s on batteries start worrying 

1 hour ago, TheBiscuits said:

 

He's no idea what he's talking about on the technical side, but he's running a 68lb thrust trolling motor on an 18' cruiser.

 

 

 

You are right he is clueless 

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3 hours ago, peterboat said:

When you have spent 1000s on batteries start worrying 

I guess it's all relative aswell. £500 for someone to buy a small new motor and two batteries to replace a £500 second hand ICE outboard would seem fair enough. I wouldn't expect a little trolling motor to replace a big inboard diesel but a good inboard is obviously a much bigger chunk of change than £500. 

 

Although the smell of two stroke in the morning is kind of nostalgic, reminds me of boating as a kid, I could go without it for the near silence and non-pollution of electric.

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my lightweight and very streamlined "canoe body" 20ft boat weighs 550kg and cruises at 3.5mph with a 40lb MK outboard.   I have 440Ah of 12v batteries which gives me 7 hours cruising with a bit to spare.  300w of solar extends the range a bit on a sunny day.

 

a typical cruiser (liked you are describing) will need more thrust than that because there is a lot of turbulence created at the transom stern.

 

electric outboards are rated in static thrust simply because it is (nearly) the best way of defining the actual performance of the propelling forces.  the actual best way is to measure the thrust in moving water, but of course that depends on the speed the hull can move at. 

the better question is: why are petrol outboards rated in horse power, and is that at the flywheel, or the prop?

 

 

e3.JPG

Edited by Murflynn
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1 hour ago, Murflynn said:

my lightweight and very streamlined "canoe body" 20ft boat weighs 550kg and cruises at 3.5mph with a 40lb MK outboard.   I have 440Ah of 12v batteries which gives me 7 hours cruising with a bit to spare.  300w of solar extends the range a bit on a sunny day.

 

a typical cruiser (liked you are describing) will need more thrust than that because there is a lot of turbulence created at the transom stern.

 

electric outboards are rated in static thrust simply because it is (nearly) the best way of defining the actual performance of the propelling forces.  the actual best way is to measure the thrust in moving water, but of course that depends on the speed the hull can move at. 

the better question is: why are petrol outboards rated in horse power, and is that at the flywheel, or the prop?

 

 

e3.JPG

I see you still carry a petrol outboard though. Range anxiety?

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41 minutes ago, David Mack said:

I see you still carry a petrol outboard though. Range anxiety?

 

yes. 

it is not unknown for a charging point to be out of order, so overnight charging is not possible, although in the last 2 seasons on the Thames I have not needed to use the petrol jobbie.

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Thanks everyone for the input. It was really helpful, convinced me that it's at least worth taking over to the boat to try out. Went today for an hour but had too many other non-boat jobs to do to have a chance to take it and give it a whirl. The boat is still tarped up from lockdown. The more I think about it the more attractive a proposition going electric sooner rather than later seems to be, given that it's only a tiny boat on a sheltered canal so things needn't be overly complicated or expensive.

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On 30/03/2021 at 21:46, BilgePump said:

Yep after that video realised how easy it would be to throw a few hundred at batteries but the other thing I'd completely forgotten about - electric discount - 25% - so about £140 saving on a licence for 18' er.

 

which is not applicable if the boat carries an emergency petrol outboard.  Catch 22.

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8 minutes ago, Martin Nicholas said:

25% electric discount applies to boats with a permanent, inboard, electric motor.

 

 

The conditions for licence rebate do not actually say that :

 

Extract from the licencing T&Cs

 

Electric Motor 25% discount if the Boat has an electric motor as its sole means of propulsion.

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Posted (edited)
12 minutes ago, Martin Nicholas said:

25% electric discount applies to boats with a permanent, inboard, electric motor.

Oh well. Not a deal breaker I guess but the T&Cs at https://canalrivertrust.org.uk/refresh/media/thumbnail/5962-boat-licence-terms-and-conditions-from-april-2020.pdf could have been a bit more specific. p20 'Electric Motor - 25% discount if the Boat has an electric motor as its sole means of propulsion'.

 

 

oops: cross posted same thing as Alan

Edited by BilgePump
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5 minutes ago, Alan de Enfield said:

 

Electric Motor 25% discount if the Boat has an electric motor as its sole means of propulsion.

Does that mean that if you carry oars as well you can't get the discount?

Edited by David Mack
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In all honesty, I wouldn't be holding any long term hopes of an electric discount anyway. I could imagine electric being the 'standard licence' with ICE tech getting some form of surcharge.

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Just now, David Mack said:

Does that mean that if you carry oars as well you can't get the discount?

 

I think you'll be OK if you cover them with  a tarpaulin and tell anyone who asks that they are fishing poles, or 'long-shafts' to push you off the 'sandbanks' that have developed due to insufficient dredging.

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