I’ve got two confessions to make right away, I’ve never used an electric on my Scamp yacht tender, and I’m not an engineer! What I have done to prepare this short review is asked Seahopper owners for their experience in using outboards and done a bit of reading around. Here’s the first stumbling block. Traditionally we’ve got used to rating outboards by their horse power! Electric outboard manufacturers start in a different place and talk about lbs thrust. The two are not directly comparable, these manufacturers will tell you, but lately I’ve seen they are beginning to give HP equivalents. So, for the sake of simplicity, I’m going to talk about motors below 1hp and those above…..
Less than 1 hp – trolling motors
First of all, unless you are an engineer or a physicist, you might get hopelessly drawn into the technicalities. For example…….
“When you look at a trolling motor rated for something like “55 lb thrust”, the figure given is often the maximum thrust that motor will give. Let’s say for the sake of argument that you’ll be going at 2 knots, or 1 m/s with the trolling motor at full power. If you’re getting the full 55 lb of thrust at this speed, then your hull has 55 lbf total resistance at this speed. 55 lbf = 0.245 kN, so (0.245 kN)*(1 m/s) = 0.245 kNm/s = 0.245 kW. That’s about 1/3 hp.”
…….but if course technicalities and physicists are absolutely vital to the arithmetic. Well that’s quite interesting is it not? So as a rule of thumb, what’s the answer to the question how does petrol compare with electric?
It’s fair to say that all thrusters or trolling motors as they are sometimes are called offer you less than 1horse power equivalent.
I’ll say that again….a maximum of 1hp. So is that enough to do the job for your Seahopper? Here’s what owners have said, and thanks to these contributors for their comments. Here’s what they said,
“The little electric motor could have been made for the boat, I bought a heavy 12 volt 70 AH leisure battery which seems to last all day at trolling speed”.
I believe Anthony, who lives in South West Scotland uses his Seahopper in still water, which is a point worth noting. Another Seahopper owner (this time a Scamp) is clearly delighted with the electric set up! Here’s what Jim from the US has to say……….
“As for this motor: It was all just total experimentation to start with! I bought a 12V trolling motor rated for 46 pounds of thrust, made by Newport Vessels, for USD $175 on Amazon. I spent another USD $125 on a Duracell 90 Amp deep cycle marine battery, and $65 more for a battery box from Newport Vessels that even has both a USB and a 12 V cigarette lighter-type connection on it, so you can keep your phone and Bluetooth speaker charged as well as powering the motor. On the maiden voyage, I neglected to bring my handheld GPS, so we decided to do a timed run at top speed over a measured mile. That calculated out to 4.5 statute miles per hour which is very nearly the hull speed of my old Cornish Shrimper! So, if we were bucking a tide flow that wasn’t running faster, we’d still have made headway, though bear in mind, this was in a flat calm in very protected waters. A couple interesting notes: In converting static thrust to horsepower, the equivalency is about 60 pounds of thrust per horsepower. That suggests this is about a 3/4 horsepower motor…………The trolling motor only weighs 20 pounds but the battery and case are nearly 60 pounds, which seemed onerous at first but we soon discovered it’s great to have all that movable ballast, nudging it around depending on gear and seating positions so you’re level no matter what. With a crew of two, set up this way, the Scamp makes a fabulous knock-about-harbor or inland lake boat, for sightseeing, camping, fishing–whatever. Last week we went out with a friend in a kayak, lashed it at the hip of the Scamp when she grew tired of paddling, and motored–mostly around half-throttle–continuously for two hours. That consumed about 15 – 20% of the total battery capacity”.
I think this is very much a thumbs up from Jim, in the conditions he uses his boat. Of course these trolling motors or thrusters are used mainly by folk who go fishing and want to move their boats slowly and silently to the right fishing spot.
Another Seahopper user Michael form the Cotswolds here in the UK, had this to say about his prevarications petrol v trolling,
“It’s an interesting idea to go electric and I looked at electric outboards at the Boat Show the same year I ordered my Scamp there. The benefit of a quiet run along a river, etc. is attractive. In the end though, we use a 13kg, 2.5 petrol outboard (with refilling its tank from a spare can of petrol on board). It seems to be quite difficult to get proper facts about electric outboards, battery requirements, weight, etc from suppliers particularly if trying to make detailed comparisons with petrol. The possible range stated seems ok for us but other sources suggest the range can be reduced if using anything more than a gentle speed. I thought there could be enough thrust from battery power but was concerned about being caught out because we use the Scamp sometimes hard against a tidal flow in river and harbour; battery weight with capacity to cope long enough may have been rather heavier than we would want when compared to a petrol engine.
Also it seemed an expensive option at about double the cost of a petrol equivalent! Plus the fuss of recharging instead of just adding some petrol and carrying on which is our usual experience with all our craft on that river and harbour area. My thinking at the moment is that battery technology has some way to go in weight reduction”.
There are many trolling motors of this type include Minn Kota, Bison, Haswing etc etc. Remember there are salt water and fresh water variants, so choose wisely. Also go for 50lb of thrust or more.
And now those above 1hp
“A Torqeedo can do everything that a 3 HP petrol outboard can, plus it’s environmentally friendly”. Well, that’s what their marketing people say. The other name you’ll come across is ePropulsion, but there are others, I’m trying to make contact with a US company that makes the EP Carry, specifically designed as an electric motor for your tender. Take a look at this review to see others https://plugboats.com/electric-outboards-less-than-5-kw/ Typically, the performance you will get (so they claim) will be something like this….
“The range generally depends on a number of factors such as speed and type of boat. If you travel slowly (4.2 km/h) you can cover up to 42 km, i.e. one battery charge will last up to 10 hours. You can travel for up to 4 hours at a speed of 6.2 km, and at full throttle the battery charge will last 48 minutes”.
Here’s a bit more data from ePropulsion about their Spirit 1.0 Plus has a 1276Wh integrated battery. At full throttle 1000 Watts, you get 6.2 mph for 75 minutes. The range is 7.75 miles. If you reduce your throttle to 25%, which is 250 Watts, you will get 4.4 mph for 5 hours.
Mark Harpur, a live aboard yachtsman, photographer and Scamp owner, regularly sends great photos and here’s one of his Spirit 1 on the transom of his Scamp. The first thing to notice is the distance from the mother ship. Here’s what Mark says about his electric experience.
“I’ve been using an ePropulsion spirit 1 plus on my scamp for the last season and am really impressed with it. It can push the boat along, albeit slowly with 2 adults using only 5 watts!
When I bought it I did a lot of comparisons and at the time it looked like the best option for the money. Better range than any of the torquedos and better price. I compared the market, but epropulsion came out top still. I have not done a full range test, but using it moderately I found that I needed to charge it once a week, which was fortunate as we couldn’t charge it onboard.
It does seem a bit heavy for the scamp, so the nose of the boat rises a bit but sitting a bit forward helps, also I don’t know what speed it gets, but doesn’t get the boat plaining. One thing I would note for others is that I got the short shaft as that is all they had in stock, but I would recommend the long shaft as there is a bit of cavitation and the prop can touch the wheel housing if turned all the way.”
On that last point if you look at the earlier photo from Jim in the US you’ll see he built his own outboard bracket arrangement, which allows him to offset the motor and prop away from the skeg – the same effect can you’ll get with our dual purpose outboard bracket accessory.
My take on this is that these motors are very good, and will provide more than adequate power and range for all Seahoppers, even for a day’s picnicking, and even against a moderate foul tide or flowing river.
I’m guessing by this point, it’s becoming clear that a big, no let me say, critical factor is to consider the duty you expect from your outboard. I’ll finish with a few points on this subject but first a few other things to bear in mind…….
Over 1 hp motors £1300-£1700 and maybe 20 kg on the stern
If money is no object and you want the environmental benefits, low maintenance and modern technology then it’s worth looking at the smaller Torqeedo and E Propulsion models……but here’s the bad news….these motors cost upwards of £1300, and that’s without a spare battery, about another £450. They are also heavy, for example the 3hp E Propulsion Spirit 1 with the integral battery loaded up is just shy of 20kg. That’s a lot of weight on the stern of a Seahopper, especially the Scamp. By the way these motors are getting bigger and bigger all the time – up to 9hp claimed, far too much for a Seahopper!
Less than 1hp motors £350 – £700 and about 15kg on the stern
By comparison a thruster, let’s take the Bison 55lb x 12volt costs about £160, plus 100amp/hr battery plus box at £150. Well below the cost of the over 1 hp breed. Ok the motor weighs 15kg, but you have to hump around a 30kg dead weight battery, but do bear in mind my friend Jim’s comment about using the battery as trim in the boat. If you’re in still water and want a decent range at decent speed the thrusters might meet your need.
Staying Petrol £400-£700 and about 13 (ish) kg on the stern
I’m pretty sure they will disappear eventually, but right now, they are the easy option still. Range isn’t a problem (unless you forget fuel!), power isn’t either as even the smallest petrol outboards will push along a Seahopper handsomely. OK they smell, they don’t always start, they need maintenance and they are noisy…….
You’ll possibly need to change the way you think with electrics. Where will you charge for example? If you’re using your Seahopper as a tender whilst cruising, charging will need a lot of thinking about. Do you really want to be hauling a 30kg battery about with your trolling motor? And do you really want to spend half the cost of your boat on an engine? Or does the prospect of near silent motoring and a motor that’s good for the environment trump the other considerations?
Here’s another thought. When you buy an electric bike you don’t expect it to do all the work for you. No, you do a little peddling. So, with your thruster, what’s wrong with the idea of doing a little rowing to ease the drain on the battery? Now, how good would that be as you skim along silently, looking for all the world like a professional oarsman?
If you’re still prevaricating about which way to go take a look at this marvellous little video, courtesy of Barnet Marine, here in the UK. It should help! https://www.youtube.com/watch?v=FLUiUioPr1A
So, what’s my next outboard going to be? Currently I’m running a 12 year old 2 stroke Mariner 3.3hp and my Scamp tender almost flies with this engine. I spend most time on the Dart with tide and stream that can run briskly at times. I also need to deal with a lot of slop and sometimes 18” waves as I motor out from the jetty at Galmpton the 400 metres to my mooring, often with gear for cruising. When my motor finally gives up, I’m pretty certain it will be one of the over 1hp models.
So to conclude, ask yourself, what sort of duty am I expecting from my outboard? Without wind, tide or stream, and the dream of a gentle day’s pottering about on the water with the family, you can look seriously at the less than 1 hp thrusters, and take the oars with you! If you need something a little more heavy duty, then you really do need one of the bigger beasts rated at over 1hp or equivalent.
Hope you have found this note useful. Please send in any comments or experience you have had with electrics and I will share these in the future newsletters.
Best Regards to all Seahopper fans!
Steven Burch, Seahopper Ltd