Electric outboards

[reeac]

Tranona, I usually recognise a great deal of accuracy in your posts, on this subject however I think you may be not looking at this from the ponit of view of how things are moving.
Battery technology is advancing rapidly, there are so many moves by governments of all persuasions to move us towards ‘eco’ options and we already have restrictions on our outboards in that we can’t buy a new 2 stroke engine, which was the best option for the small 1.5 - 2hp market, they are relatively light, more efficient than a 4 stroke and cheaper to produce.

I'm not sure about the "more efficient" claim. Traditionally the figures for bhp hours per gallon are: diesel 20, 4 stroke 15 and 2 stroke 10-12. The latter tends to suffer from incomplete combustion of the fuel due to the tricky gas flows in and out of the combustion chamber.

 

[Praxinoscope]

I'm not sure about the "more efficient" claim. Traditionally the figures for bhp hours per gallon are: diesel 20, 4 stroke 15 and 2 stroke 10-12. The latter tends to suffer from incomplete combustion of the fuel due to the tricky gas flows in and out of the combustion chamber.

Perhaps I should have said that cubic capacity size for size a 2 stroke gives about 40% more power output per cc than a 4 stroke, I still remember my old rallying days when my SAAB GT 750 would out perform cars with 4 strike engines of 1200- 1400cc.
Agreed fuel consumption is higher, if I really pushed her to the limits my fuel consumption would drop to about 14mpg.

 

[wombat88]

Nothing beats the sense of security you feel as you push against the tide with a leccy outboard and can hear the revs gently dropping...

 

[JohnGC]

I think it's probably "very good" because it's basically a direct copy of the Torqeedo!

It uses a significantly different motor technology and doesn't have a gearbox. Apparently, eProp was set up by ex Torq staff .

 

[JohnGC]

Nothing beats the sense of security you feel as you push against the tide with a leccy outboard and can hear the revs gently dropping...

Have you had that experience? I'd be interested in the details.

 

[pvb]

It uses a significantly different motor technology and doesn't have a gearbox. Apparently, eProp was set up by ex Torq staff .

Yes, it uses a simpler and cheaper motor technology, but still claims similar efficiency ratings.

 

[Plum]

I'm not sure about the "more efficient" claim. Traditionally the figures for bhp hours per gallon are: diesel 20, 4 stroke 15 and 2 stroke 10-12. The latter tends to suffer from incomplete combustion of the fuel due to the tricky gas flows in and out of the combustion chamber.

It certainly is possible to make a 2-stroke more efficient than a same displacement 4-stroke.

Www.solocoastalsailing.co.uk

 

[MikeBz]

I think it's probably "very good" because it's basically a direct copy of the Torqeedo!

In that it's an electric outboard motor yes... Hardly a direct copy though. Differences here: https://nestawayboats.com/shop/e-propulsion-spirit-1kw-electric-outboard/

 

[pvb]

In that it's an electric outboard motor yes... Hardly a direct copy though.

Just looking at the design will certainly lead most people to think it's a copy. As for the differences, it has (as I said in post 26) a simpler motor, otherwise (apart from no GPS) it's much the same.

 

[reeac]

It certainly is possible to make a 2-stroke more efficient than a same displacement 4-stroke.

Www.solocoastalsailing.co.uk

I assume that you're referring to bhp per litre of displacement, not fuel efficiency. If the latter were the case then car manufacturers would go 2 stroke in this eco environment.

 

[Porthandbuoy]

All the electric outboards I have seen eem to have very long shafts which make them rather ‘strange’ to use on a small inflatable or dinghy.
Unless there is some technical reason which I can’t see there must be a market for short shaft electric outboards?

I have one of these ‘trolling motors’. As you say, the shaft length makes it uncomfortable to use. I took it apart and shortened the shaft so it is now the same length as my Yamaha 2hp 2-stroke.
The electric motor is great for silently exploring a quiet anchorage and sneaking up on wildlife, but for windy / choppy days the 2-stroke wins every time.

 

[rotrax]

It certainly is possible to make a 2-stroke more efficient than a same displacement 4-stroke.

Www.solocoastalsailing.co.uk

Not true.

It is possible to get far more power from a 2 stroke engine of the same capacity as a four stroke.

But, going back to basics, efficiency is work done over fuel used.

Four strokes win every time on efficiency, but not for power output.

On a schnurle loop scavenge two stroke, the exhaust system is a major part of power output.

With a deflector piston two stroke, not so important, but piston weight/shape limits revs.

All have shortcomings-shortcomings not shared by electric motors.

 

[Praxinoscope]

Not true.

It is possible to get far more power from a 2 stroke engine of the same capacity as a four stroke.

But, going back to basics, efficiency is work done over fuel used.

Four strokes win every time on efficiency, but not for power output.

On a schnurle loop scavenge two stroke, the exhaust system is a major part of power output.

With a deflector piston two stroke, not so important, but piston weight/shape limits revs.

All have shortcomings-shortcomings not shared by electric motors.

Surely part of the reduction in ‘efficiency’ of a 4 stroke is the additional ‘machinery’ required for it to operate, (camshaft, valves etc. ) all creating their own friction/effort thus consuming energy from the combustion.
Electric outboards must surely be the route to go but like electric cars they need to have the range, power and affordability of petrol based engines whether 2 or 4 stroke?

 

[UMCorps]

Probably not immediately relevant to the original poster's question but there are a couple of important things about using electric outboards when sailing that can get overlooked.

First is that with both the Torqeedo and Epropulsion style of motor, the "pod" housing the motor, prop and skeg is considerably longer and fatter than the equivalent on a petrol outboard. If you mount your motor in a well rather than hanging it off the back you need to check it will actually fit. The well on my boat is too tight. The only way for me to fit a Torqeedo there is to remove and then refit the prop. Which is not much use if you are on a mooring most of the year.

Second is that the documentation for both engines cautions very clearly against allowing the prop to cycle when it is not being driven by the motor. (I assume this is to protect the battery and charging circuit from potential reverse voltage. Someone smarter than me will probably be able to explain why this can't be done by better circuit design.) So, when under sail, you need to have quick, easy way to lift the engine and its prop clear of the water and keep it out of your way. Which is easier in some boats than in others.

 

[Sailfish156]

Hi Guys,
Thanks for all the comments.Yes I have a Sailfish 18 and several of the Sailfish association members have electric outboards and find them quite effective - as long as you recognise the limitations.
Going through the thread I see no one has commented on the durability or issues of use in Salt water? Any info appreciated.
Phil
Sailfish156

 

[rotrax]

Surely part of the reduction in ‘efficiency’ of a 4 stroke is the additional ‘machinery’ required for it to operate, (camshaft, valves etc. ) all creating their own friction/effort thus consuming energy from the combustion.
Electric outboards must surely be the route to go but like electric cars they need to have the range, power and affordability of petrol based engines whether 2 or 4 stroke?

I think you are missing the point. Four stroke engines ARE more efficient than two strokes despite the mechanical losses you quite correctly point out.

In the first line of your reply you say " Surely part of the reduction in 'efficiency' of a 4 stroke "

What reduction in efficiency compared to a 2 stroke?

IIRC, a good measure of efficiency-if not the only one-is work done over fuel used.

4 strokes win hands down.

 

[noelex]

I am in the market for new small outboard.

The electric models such as Torqeedo and Epropulsion have appeal. The initial cost is not such as big problem if the product performs better, but I cannot come to terms with battery cost.

A single battery, on its own costs much the same price (or more expensive) than the equivalent four stroke petrol outboard.

Given constant use of full time use of a cruising sailboat 5 years seems a realistic replacement schedule for the battery. Even if never serviced a four stroke outboard would probably last as long. So there does not seem any advantage in terms of service costs, although a simple oil change would extend the life of the petrol outboard considerably and it hard to imagine an owner not doing this.

 

[thinwater]

There are a number of reviews in Practical Sailor Magazine, including trolling motors.

By my read, the greater concern may be running them flat-out for long periods. They arn't built for that.

 

[pvb]

Given constant use of full time use of a cruising sailboat 5 years seems a realistic replacement schedule for the battery.

I'd expect much longer, assuming the battery is properly cared for in terms of recharging. What will happen is that the capacity of the battery will decrease gradually over the years, but this might not adversely affect the average user. The battery packs on electric cars are typically guaranteed for 8 years - and this is a guarantee that they'll retain something like 70% of their capacity at the end of that time. I expect my Torqeedo battery to give me at least 10 years service.

 

[RupertW]

I am in the market for new small outboard.

The electric models such as Torqeedo and Epropulsion have appeal. The initial cost is not such as big problem if the product performs better, but I cannot come to terms with battery cost.

A single battery, on its own costs much the same price (or more expensive) than the equivalent four stroke petrol outboard.

Given constant use of full time use of a cruising sailboat 5 years seems a realistic replacement schedule for the battery. Even if never serviced a four stroke outboard would probably last as long. So there does not seem any advantage in terms of service costs, although a simple oil change would extend the life of the petrol outboard considerably and it hard to imagine an owner not doing this.

I don't think there is a good case to be made for electric motors on cost - you are buying into a completely different proposition and either it works for you or it doesn't. The reliability and ease of use is important - it's not so much that you don't have to pay for the service but that it will keep starting just by turning the throttle with no maintenance - if you ever have crew who are nervous about a pull start they will never need to be again. And add in the fact it's so clean it can be stored on a bunk once you washed the salt off and refuelled from the ship battery then the costs seem less relevant.

Finally on the battery life - I don't know how much longer our 4 year old battery will last but there is no degradation at all evident so far - however the replacement battery is already almost twice the capacity of ours and we've never had a range problem so a 5 yearly replacement is actually a 5 yearly massive upgrade at the current rate of progress.