Review of
The Bison 
Electric Outboard

   100lb Trolling Motor 

Welcome  to my review of the Bison 24 volt 100 lb electric outboard trolling motor. 


I have decided to produce this review for those like me who wanted to use it as an outboard motor on a lightweight GRP motor cruiser. The only reviews I could find were short and not terribly informative. Certainly way short of what I wanted to see and nowhere near enough to make a balanced informed decision about the wisdom of purchasing one for my boat . It looked as if the Bison 100 lb trolling motor would suit my needs but I would have to be my own guinea pig.


The trials I have given it aim to produce  very much close, but, it must be remembered that they are  approximate figures.  Rigorous testing would be preferable but Hey ! no one pays me to do this. It has been written  for the benefit of those who know little or nothing about the subject. So remember these are my figures for my boat and are only designed and should only be used for rough guidance purposes.

The Bison 100lb Trolling Motor


The Bison 100 lb is the largest and most powerful in the Bison range. If there had been a more powerful motor I would probably have bought that just to be on the safe side, although I felt sure that for the purposes of inland cruising on canals or at most very slight current from a river  the Bison 100 lb will be sufficient.  Rivers like the Thames or similar. I think not.  

The Boat 


The boat is a GRP 30ft Dawncraft with a modified wooden top.This means its a little heavier than the standard GRP Dawncraft, but it is still a lightweight craft especially when compared with a steel boat of a similar  size.


Engine Power


Power is provided by 2 by 110 amp hour leisure batteries connected in series. They have to be connected in series and not parralel because this size Bison motor operates on 24 volts. This size boat could, if one chose easily accommadate 4 batteries or more if desired thus providing a greater cruising distance.


Battery Power 


Battery power at the moment is provided by 1 by 100 Watt Solar Panel. For extensive cruising on a daily or near daily basis this is not enough. For such purposes 2 by 150 watt panels would I imagine be needed. Possibly more but at the moment I cant say. I will be buying, in the near future at least 1 more 100 watt panel. It would be appreciated if at some time someone would let me know what I should have bought.


Winter Cruising 


I only do short distance moves at most in the winter and solar panels will not produce anywhere near enough power to be used for lengthy daily cruises. A back up system power supply provided by a generator will be required in the winter for extensive cruising . 


The Tests 


The tests will be based upon speed per mile at each setting  and distance per battery charge. They will be performed on the Grand Union Canal and on a day or days with very little wind from any direction. 


Pre - Test Issues 

1) Very poor wiring instructions for the Circuit Breaker, which incidentally I suggest is essential and should  perhaps be provided. The instruction booklet says to wire the negative directly to the battery and the positive to the circuit breaker and then to the battery. The label on the motor says to do the opposite. For the record it is negative to the battery and positive to the circuit breaker and then to the battery.  


2) Given the instructions about keeping the motor dry because of the possibility of water ingress, arguably a tailor made waterproof  cover should be provided.  


3) The supplier has recommended that the engine is not left in the water for extended periods of time due to the possibility of water ingress. If this is the case it might have been an idea if the seals were of a more durable quality, after all they are not the most expensive item but there ability to prevent water ingress is crucial.    


4) A reasonable sized metal "O" ring through which to thread some chain and a padlock would have been nice   


Advantages and Pleasures in Brief 


1) Without any doubt cruising without either smelly or odourless fuel exhaust fumes is an undeniable pleasure.


2) Without any doubt cruising without much / any appreciable noise at the lower speed levels is also an undeniable pleasure.


3)  Although there is an initial set up cost with panels and batteries  it is not long before the costs of fuel quickly begin to be offset by the amount of free cruising.


4)  Time will tell but the supplier assures me that these motors require very little if any attention. All petrol outboards will have a basic servicing cost each year  and not inexpensive repair cost. At about 60 pounds per hour plus parts 3 hours of repair/servicing pays for a new electric outboard .


5) The engine is very light and can easily be fitted  on and taken off.  In complete contrast to an outboard which is a heavy awkward lump for anything of a meaningful size and I think is best done as a two man job. 


6) The engine itself is very cheap at 200 pounds  to buy.


7) On Canal and River Trust waterways there is a 25% reduction in the licence fee  which

almost pays for the engine in itself! (Correct at time of writing April 2019)



8)  There is no need for  having highly flammable fuel on board. 


The Tests

The speed tests were conducted early in the morning on a ccrips but sunny morning with very little if any wind  1 measured  half mile at speed setting 5 took 12 mins. 10 secs. giving a speed of   2.479 mph

1         "             "     "     "     "           "      4    "      13     "     28   "          "      "      "     "     2.259  mph 

1         "             "     "     "     "           "      3    "      15     "     20   "           "       "      "      "     2.027  mph   

1         "             "      "     "     "           "      2    "   18       "      10   "           "        "     2      "     1.657  mph


No test was done for speed setting 1 because it is very slow.     

The Maiden Voyage 


Up very early, its a fine morning. Began procrastinating with one tea after another, followed by breakfast. About 10 ish set the engine up on the transom and then connected the leads to the 24 volt battery arrangement. Would it work? Why wouldn't it. Of course it did. A very, very quiet hum even as I was a couple of feet from the motor itself  An immediate problem is identified. Steering this is not as as easy as I would like. The extending arm does not extend very far and is soon pushed back into place by the tiller I have fashioned. In the long term something will need to be done about this. Its not a fault of the manufacturer, its me putting the engine to a use not envisaged.             


Delightful voyage of 1 mile. Amazing, its almost totally silent in the lowest setting and not much louder in its highest . I can hear people speaking on the towpath, the bird noise  in the trees or on the water. There was even what sounded like an alarming splash behind me. It was just 2 coots arguing. I can listen to T.M.S. for example at a normal volume instead of louder than I would like to in order to overcome engine noise. 


I would have gone further but my 2 test batteries are 2 old ones close to finishing point. One is a starter battery and one a leisure battery which is not an ideal mix. 


I tested all speed levels. At lower speeds the boat tends to wander a little more. The higher speed levels are at   speeds  that are  perfectly adequate for inland canal waterways cruising. Top speed is a speed that would be considered  too fast for passing moored boats at. 


I have not been far but  under no circumstances could I recommend cruising  upstream of a river like the Thames. Whilst I think it possible to move along at top speed, progress would be slow and there is always the potential the higher up one goes of stronger  currents, especially after a lot of heavy rain. One summer a few years ago now, the Thames was closed for weeks and weeks because of the amount of rainfall in the form of very heavy showers making cruising dangerous.  I heard that one boat actually  became stuck high and dryish on a weir. It is i think highly inadvisable to travel against tides and current in areas and rivers such as the Norfolk Broads.   


But that is the Thames, Norfolk Broads and similar. My next short cruise will be along a short stretch of canal into which 2 small streams enter.  It has very slow moving water and should cause few problems. Its also very clean and clear freshwater, which means there is a lot of marine vegetation growing in the water. Huge green leaves waving around beneath the surface.   


The Second Test 


This second test is necessary to see how the boat engine performs against a modest  outflow current  and travelling upstream against a downstream flow. How much of a struggle at full speed is it.  


In actual fact on the day of this test there was also a bit of wind against me, just to make it a little harder. I put the boat into speed setting 2 and moved off. Not terribly far and not terribly fast, but progress against wind and current at a slow speed setting  is possible. Obviously progress will be better at a higher speed setting.


More of a problem was mooring up with the wind and current behind me a widebeam boat to pass by and only a small space after to moor in at the precise moment the battery is about to fade away. Moral. Try to be aware of how much power is in the battery.  


I have spent a short time practising reversing. The boat can be turned  180 degrees almost on its own axis. Its not particularly potent at any speed setting in reverse but it moves the boat. This fact is one reason at least for not fitting to a heavier steel? boat. The lack of reverse thrust power makes stopping quickly unlikely because of the forward momentum. 


Below is a photo of the first stream's outflow. A current can be seen as it discharges. Above the lock water flows over the gates and is usually a sure sign of recent rain thus adding a small amount more to the downward current. 




















The Third Test


The third test  is to see how far the boat can travel before the two 110 amp hour batteries  batteries need recharging. The test will begin just below Cowley Lock and I will go as far as possible into London. This a distance of approx. 23 miles with no locks. I will travel at speed setting 3. I do not like just standing all day long so there will be stops every couple of hours or so but the batteries will not be recharged at all. The solar panel also will not be connected to the batteries. This is because the panel's input will vary depending on how much sunlight there is; is it cloudy or sunny, do I travel at dawn or midday to name two adequate reasons.   


This test began at 5.30 in the morning on a quite beautiful day. Speed setting 3 was originally chosen but because the propeller soon became clogged up with weed speed setting 2 was used. When clogged up one feels an immediate loss of power and when looking at the engine its obvious by the way it seems to start and stop, again and again that something is wrong. Its a simple but slightly disgusting task to disentangle the mixture of rubbish and weed. A few times old carrier bags were met with. These puller the tiller one way or the other and are then gone. I now only travel at speed settings one or two. 


There is a lot of floating rubbish in the London waterways. In places it really is absolutely disgusting. Shame to say but looking at the way black bin bags are left neatly tied up  en masse beside the towpath I would guess that it is boaters leaving much of the rubbish, Its not just boaters of course leaving their rubbish for someone else to pick up, there are the fisherman, the drinkers, and not to be forgotten the dog shit bag leavers. What possesses someone to pick the dog shit up in a plastic bag and leave it either hanging on a tree or chuck it in the canal. 

       I did not go as far as I would have liked. 3 miles max. was the distance traveled on 1 charge. 2 sets of batteries are therefore recommended. Recharging is dependent upon solar but in good sunny weather each battery takes about 5 or 6 hours to recharge with the 2 panels I have.


The Fourth Test


The fourth test will be an assessment of performance over time and will appear perhaps in September.


I had proposed to do an extended cruise from London to Oxford. However the difficulty with moving westwards out of London has meant that this section may not appear until next year.   



 There is no doubt in my mind that electric engines such as this will become more and more popular. Cheap to buy, economical to run, environmentally friendly, lightweight, quiet and  together with the predicted, soon to happen improvements in battery storage capacity and increased battery recharging speeds etc they are the future. It would be helpful if CRT would introduce battery recharging  facilities at say water points  but, regrettably, I would be very surprised at CRT doing anything, anytime soon of assistance to boaters.   


The 100lb trolling motor on smaller GRP vessels for example the 18 to 25 foot range will of course be speedier than mine and presumably travel further. Having said that for the extra expense of another battery and the higher price of the larger trolling motors even if the smaller engine would suffice  I would say "Get the larger engine" you will not regret having a little more power but you might well wish you had a little more power.


Sooner or later I envisage that 150 and 200lb trolling motors and quite possibly even more powerful motors will be available although I suspect they will be running off 36 or 48 volt battery systems. If a larger motor  had been available I would have bought it instead. Perhaps my next one.  


The solar panel set up I have is probably not what those who know about these things would recommend for the task that  has to be done. Advice as to what should have been done will be gratefully received.


Solar panels are fine in the summer months and even if cloudy batteries can still be recharged,, perhaps a couple of days. But in winter it could take a fortnight maybe longer. Solar sounds a great idea until the reality of available sunlight in winter is fully understood.  just about useless.

I can confirm that winter travelling is crap when relying solely on the sun for battery charging.  Batteries accept less charge, it takes ages to charge,  the maximum ampere input is very low and the maximum input does not last long.  On the plus side, unlike with 2/4 stroke outboards there has never been any issue starting on really cold days.  


* Had I known then what I know now about solar I would have bought 2  by 350\250  watt  panels  or similar rather than 2 and then 2 more 100 watt panels.   

Bison 100lb Trolling Motor   


Below is a photograph of the Bison 100lb trolling Motor attached to my boat and taken in Paddington Basin. The engine has been in the water for 5 weeks or so.  It is perhaps a little lower in the water than I would ideally like but it works. Underneath can be seen a green plastic bag, a modern day blight . On the surface of the water is duckweed; another modern day blight. The water itself however is very clear.  


The date today as I write this is July 4  2019.  I have encountered a severe problem with this electric motor. It is terrible when travelling through blanket weed. It becomes entangled so quickly whether in forward or reverse. I highly recommend that where there is any expectation of blanket weed DO NOT GO THERE!!!

 In London at the moment blanket weed is not the only problem for these electric engines. Over the last 6 weeks or so there has been a steady build up of duckweed. 6 weeks ago it caused few problems and was easily brushed aside, but now it covers the whole canal and is growing increasingly thick. It does not stop one moving but it causes a frictional resistance that ensures slower movement for the same power usage. This is ok for short hops but of course whereas one could get 4 miles from one set of batteries this distance will be reduced. Its not possible for me to suggest a figure because I can not move more than a few yards   because of the blanket weed. 

Above  is a picture of the propeller taken out of the water after travelling about 20 yards forwards  maximum and punting back to the bank side. Nobody is going far with a propeller clogged up in this fashion and this quickly in these conditions.  












Above is duckweed at Kensal Rise stretching right across to the other bank

In the last few days  in early to mid March 2020 2 further issues have presented themselves.  The 1st is that one of the fins of the propeller has snapped off.  This results in the engine vibrating.  I imagine this to be a common occurrence which is why 2 propellers  are included.  This has been caused by movement of the boat whilst moored in water that is very shallow and leaving the engine in the water.   The 2nd problem is the locking mechanism.  This no longer works properly.  The probable cause is probably also movement of the boat in shallow water and the consequent strain being  placed upon this mechanism and breaking a part too weak for the task.  It has too be said though that the engine quite probably was only ever envisaged too be on a modest dinghy sized boat rather than a 30 foot GRP cruiser.   

It is now  over 1 year since I  first bought the Bison Engine .  Overall I would say that I am very pleased with its performance  although there are issues.  To some extent the issues are in part my fault,  but weak design and build quality in crucial areas with moving parts do not help.   

It is now August 2020 and a further issue has presented itself.  In order to change up or down a gear or into forward, reverse or neutral the tiller must be rotated.  From day 1 I have always suspected that this was of  flimsy construction and liable to breakdown far sooner than it should due to being unfit strength wise for the tasks and purposes  to which it is entrusted.  

The biggest disappointment about this outboard apart from not being able to buy one with a short shaft option has been the now realised suspicion that moving parts that need to have been built with the strength to withstand the stresses and strains of even reasonable backwards and forwards movement without failing.  If I had to guess I would guess that whatever the key part/s have been made from plastic.  But I pre - empt.  

September 15  2020

The engine has now ceased operating altogether.  I suspect that the cost to repair will almost if not actually outweigh the cost of buying a new engine.  I will be contacting the supplier to see how things stand with regard to repairs needed and likely cost and report back.   

October 6   2020

I have now contacted the supplier  about the required engine repairs.

1)  The locking mechanism 

       My understanding is that this has an inbuilt "T-Bar " designed to snap when placed under significant pressure ie. by grounding in shallow water.  This is to prevent damage to the main shaft.  The cost of a new "T-Bar" is 4 pounds and can be done quite easily.   This is quite probably what happened to mine.  This was also liable to happen sooner or later  in shallow water when using an engine when the shaft is too long.  Why no Short shaft option?


2)    Stuck in one gear 


    This also is supposed to be quite easy.  I'm told it is one of two possible parts but i n order to see which I will need to detach the top and send a photo of the internal workings to see which.  The part is about 15 pounds  and also should be within the scope of anyone with only modest mechanical capability.        

3)    Wont Go 

Probable burnt out switch.  Again about 15 pounds and should be within the scope of anyone with only  minimal mechanical understanding.

However returning the item for the seller to repair will of course incur delivery charges to and from plus labour charges.  If you cannot or dont wish to do it yourself its probably best to buy another unit with 12 months guarentee etc.   

If you decide to buy one of these engines I would also recommend choosing your supplier with a little care.   A good supplier in 13 months time and the guarentee has run out can, if there is a problem,  offer knowledgeable help and assistance.   A poor one will not be remotely bothered.  




Thank you for reading my review. I hope it was of some use or at least quite interesting  

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Thank you for your time 

Nigel King


Above is a picture of the huge branch. 

I will have to stay a few days in Ricky  awaiting 2 solar panels. I have decided that if I want to go to Northampton  in anything like a sensible time scale these 2 extra panels are essential. 


August 19


Left Ricky today and made it all the way the way to Hunton Bridge. I have never seen quite so many boats in this stretch.  There was a time 10 years ago there would only ever be a few boats.  Those days are gone.  The way things are going the day will come when  it will be one continuous line  of moored boats  between Hunton Bridge  and North Grove.


Before I left Ricky I had a quite a good look at a book by Ian J.Wilson  The Grand Union CanaI  with many good life as it was lived photographs going back over a century.  As one might expect  there has been a lot of change over the years but much is still there and recogniseable.  I found it interesting also took at how well  the vegetation has been managed.  On the towpath side it has been kept very much under control.  Wide towpaths 8 or 9 feet perhaps more  usually with either a neat  cut and laid hedge or just open ground.  Very few trees are to be seen on the towpath side at least.  No leaves or small twigs and branches into fall in the  the water.  No huge trees  to be chopped  up as they fall and die.  No consequent sediment build up thereby necessitating dredging.  No overhanging branches etc.  It's a far  cry from today's miserable, lamentable  efforts.  As I write this paragraph the hedge right beside me has overgrown so much that there is now only about 2 feet of towpath left. 


It  is a different story the other side.  More trees, more vegetation, trailing into the water but nothing like today.


Another point that is very noticable are the views around corners.  Most of the time nowadays whether on the left side or right side towpath  most corners  to the left or right and either left or right with anything like a decent curvature are now blind corners.  One cannot see what is coming beyond the corner from the other direction.  In almost all photographs  where the towpath is on the left  and there is a leftward bend it is easy to see beyond the curve and into the distance and observe anything coming in the opposite direction .


There are places today where the vegetation growth is under control.  This is mainly where there has been  some development. The area where Dickinson paper mill wharf above Common Moor lock is one of the best  Barely a weed is growing out of the bank side. 


Literally just around the corner is yet another example of willow trees running amok.  On the towpath side is a huge albeit pretty hanging willow hanging right out over the canal.  On the other side the willow crack or snap willow has fallen rooted grown  so much that in and in places it is now not  possible for a widebeam to be moored and leave enough clear room for another to pass.  This is a decent length of long term neglect. I shall be surprised to learn that anything is to be done about it this Autumn but who knows 


A few hundred yards further on is Croxley Marina run by P. and S. Marine.  This modest sized marina is where I bought my first boat 25 years ago.  I moored in here for a few weeks until the owner realised I was living aboard.  I left the day a bill for residential mooring appeared.  Had I realised how much more rewarding it is to be outside the marina rather than inside I would have left the day I bought the boat.


This marina is the drop off point for new boats who are basing themselves around the London area and in particular widebeams.  The cost to be craned into the water, perhaps an.hours effort at most ...a whopping 700 quid.  Once in the water beginners have to negotiate there way in their brand new shiny boat out of this small marina and onto the cut This kindly ,generous spirited pair of scalkywags can assist and the boat out of the marina and onto the cut for a further 50 quid !!!  


Just before Croxley Lock is a disgraceful example of the way CRT ignore maintainance work that really should be attended.  A photograph is below.


Apsley lock and its "Wild Flower Arrangement"