Fitting an electric outboard to an inflatable kayak / canoe

As this post now already has a three photo evolution of the Outboard Chariot, why not the final working prototype? Here she is! All the hoped for adaptions working with a few new ones on top!

Update June 2020 – Final prototype, post-assembly. The Mk. V now has wheels! Next step to test with battery and motor attached. Pulling handle currently just loops of paracord. Just need some wing nuts to be able to quickly remove/assemble wheel mount and I’m done for now. Link to more photos here.

The series of posts about this development contains side and rear mounted motor mounts. All have their merits and provide a base for creating your own design to fit your craft. The side mount gives the easiest access to control, as the rear mounted versions all require uncomfortable stretching to reach the throttle bar. A bit of plastic pipe, split at one end and then taped over the throttle is a simple way to get around this (can’t recall where I saw that in a post years ago).

Ahh, I’m awake, the sun has returned! Final update to this post before it is just a bunch of links! April 2015 – Here it is, as pictured below, before final testing The Mount The Iron Gym method still gives the best cheap DIY base offering the various design options you can try.

Link to second installment including trolling motor comparison research and more links for spares/kit.. Now with all amp draw ratings for Bison motors kindly provided by Craig at Fishing Mad

Update: 24th July 2014 – Here’s a photo of the motor mount prototype Mk. III. Basically, this is designed to be mounted at the rear of the kayak and I’ll be giving it a field test this weekend. It is simpler, more compact and removes the need for the battery to balance the mount. So far, it has taken the full weight of the 62lb Bison motor, out of the water, without straining the bladders and feels more secure than the Mk. I already. Will post results and photos or a video on the build and installation into the kayak once testing is complete. (Still using mostly the same basic gear as in this post)

30th July 2014 – Link to latest test results on this aft motor mount – best design to date!

Hmm, I didn’t think my first ‘how to’ guide would be in this vein, rather something akin to the recent bug I uncovered in Backup Exec 2012. Ah well, I did also say I’d only do so if I couldn’t find any similar online guide and for some reason mounting an outboard motor on an inflatable kayak isn’t a common occurrence.

I’ve messed around with boats of one kind or another for most of my life and love spending time in, on, by and under water. I haven’t recently had the chance to do so and I thought rather than rent a canal boat for a few days as a holiday last week, I’d spend the money on a kayak and electric outboard.

I’d first tried out an electric outboard at Henley Regatta in 2009 and was very impressed by the smooth, silent running, let alone the number of glasses of Pimms and champagne shared with people on shore intrigued at how I professed to be piloting a ‘solar powered’ boat. (I was charging the leisure batteries back on shore each day with a small 60W solar array from Maplins) The silence of the motor when trolling back at 1am to my mooring allowed me to witness ducks asleep on the water undisturbed until I was nearly a metre away from them! Something I had never seen in all the years of paddle or combustion engine boating.

On spending a day out on the Thames in the new kayak last week I really began to strongly feel that conversion to electric motors should be made mandatory on British waterways for many leisure and entertainment craft. Many moorings already have mains power to them and craft sit idle for long periods so this wouldn’t be a difficult change to enact for so many obvious benefits.

Anyway, on with the guide. First the caveats.

I in no way suggest that you are crazy enough to do what is outlined in this guide unless you choose to do so entirely under your own recognisance and taking responsibility for your own actions. I am merely sharing an idea I have tried in order to add to other’s inspiration in trying their own concepts.

I treat any excursion on water with extreme care and respect for the dangers inherent and strongly suggest the same for anyone else. Check tides, currents, weirs and weather conditions and often even better, talk to the locals if you don’t know the waters you are travelling on. Wear appropriate garments and protection.

In any small vessel, I always find that slow, considered movement is the key to remaining dry and in your vessel. Plan what you want to achieve, do so slowly and smoothly and you will minimise any dangers.

The Build – Background

My aim at the start was to provide a cheap, simple and light platform to mount an electric motor on to an inflatable kayak and ensure I could carry the full kit by myself from car to launch point and in the kayak.

I liked the look of the Adventure Plus kayak and with the new ‘backpack straps’ it seemed ideal (They’re not exactly comfortable but also not presumably designed for long use). I put in the orders and now the only thing that remained was how to mount the motor.

I had seen various methods employed on rigid hull canoes and kayaks but the only ones I saw that look viable (and I am still considering trying) were using plastic boxes like milk crates to hold a battery that had a couple of wooden boards overhanging to the side/back that the motor could mount onto. The principle of using the weight of the battery to counter the weight of the motor being an ideal bonus.

My only other consideration at the time was to build a hinged wooden box/shelf contraption that would again balance the battery against the motor but fold down for easy transportation. Using a good hardwood for water tolerance made me feel that this may be too cumbersome or heavy to be viable for transporting. Cost would also factor.

Investigating further, I noted a rounded metal rod based mount on an inflatable RHIB that looked like a modified fender holder with some marine-ply bolted on for the motor mount. The curve of the metal rods, fitted well around the hull of the RHIB and appeared to either be fixed or counterbalanced inside the RHIB.

I then saw that my door mounted chin-up bar had a similar curving and a cross bar that reminded me of motor mounts I’d seen previously such as Intex make. I grabbed the motor, wound the grips to their fullest extent and failed to grip the plastic cross bar. Still, the principle seemed sound and upon inflating the kayak and placing the chin-up bar in the kayak, it slotted in as if it were made for it. I then purchased a length of timber to test further both on and off water and am now at the stage of making some final tweaks to get it finished.

I have now tested the mount twice and although I am not entirely happy with some aspects, it is entirely fit for purpose and most importantly works in terms of balance, control and stability. As the final improvements will require my ‘Dremmelling’ skills, I am considering if trying to make my own tubular supports that provide the exact frame shape I require is a better aim and to leave this working prototype as is so I can use it as a chin-up bar again! (I’m also looking at making a frame for mounting simple outriggers next)

Parts Guide

• 1 x Sevylor Adventure Plus inflatable kayak – Simply Inflatables
• 1 x Bison 62Lb thrust electric motor (overkill but to be used on other vessels so go with your preference) – Fishing Mad. They do all sizes of Bison motor and now a Bison battery box
  
• 1 x Halfords 70Ah Leisure (Deep Cycle) battery (or similar battery of personal preference)
• 4 x Bungee cords (2 x ~30cm, 2 x ~70cm)
• 1 x Pro Fit Iron Gym chin up bar (Yes, really! I think I got mine at Robert Dyas ages back but you’ll probably have to try Ebay..) – Official site 
• 1 x Wood beam ~ 45 x 5 x 5cm (Teak/Iroko or your preference)
• 2 x Nut/Bolts/Washers M6 diameter (I used 100mm for testing which are a bit long)
• 1 x Box/tray to sit battery in (I would consider/suggest a proper battery box to keep battery and connections dry in case of rain or splashing Bison battery box)
• 1 x Piece of foam/cushioning to put between motor mounting base and kayak hull

Tools

• Drill
• Number six wood drill bit
• Spanners/pliers to tighten bolts

Build – Modifying Frame

When receiving your ‘Pro Fit Iron Gym’ you would need to assemble it. Build as per the guide and then rather than fitting the plastic bar, use the plastic bar as a template to drill two holes in the wooden beam you purchased separately. (I used a size 6 wood drill bit)

Fit the wooden beam to the bars above rather than below the metal fixing locations as in the photo. It is better to have the excess bolt pointing upwards rather than down to avoid puncture/tear concerns.

Inflate kayak!

Slide (let’s call it the mounting bar) the mounting bar into the kayak with the rearward pointing bar sliding under the splash guard and the front of the bar fitting under the rear seat strap. (The two vertical bars rest on or beside the inflated floor and are one of my concerns in terms of their being too long and creating two, high pressure points on the inflated floor which are the pivots for the whole assembly.)

Place battery (in box or on tray) into rear of kayak behind the seat and in between the two vertical struts of the mounting bar. Hook and loop longer bungee cords under battery, crossing over and coming back to the end of each vertical curved bar on the mounting bar (there are two holes in the plastic end pieces on the bars that the bungee hooks fit into perfectly).

Hook and loop short bungee cords to battery and affix one end of each to the backpack strap clip under the splashguard and the other to the clip for the seat support. (Please note, I realise that the Halfords batteries have carry handles that make this easy where other battery makes may not)

Mount motor on wooden part of mounting bar, tighten and adjust angle. Then lift motor mounting and place foam between mounting and kayak hull. Finally, connect battery. Note: The photos don’t show the final 5 x 5 cm strip of wood hence the motor tightening screws overhanging.

Zoom…!

I didn’t put it in the part list for the build but this trolley is perfect for loading the battery, motor, backpack, pump and other bits. It then folds down and stows easily in the kayak. The full kit above weighs in at under 50Kg and with only the kayak’s 14.5Kg on my back, the rest fits onto the trolley.

Testing

Well, no point going to all of this trouble without seeing if it worked! Last week I took the whole kit out to the River Arun and launched at Pulborough slipway. As a first taste of a tidal river I certainly messed up the tide timings and ended up launching in about three inches of water surrounded by various obstructions sticking out and threatening my lovely new kayak hull.

I didn’t obviously mount the motor until I’d reached a deeper section and had moored to a sunken tree but once fitted, ran against the current at about level one on the motor mostly, running up to level two or three at heavy flow points.

As I was completely unaware of the river depths, I mounted the propeller quite high and only ran into heavy underwater plant life a couple of times, posing minor navigational problems. After a relaxed trundle up to Stopham and back, taking about three hours and using the motor for about two, the battery still registered at nine out of ten on the Bison battery gauge.

Considering at that point I had also used only long wood screws to fix the wood to the mounting bar, I felt it was a complete success. Landing at 9:30pm at really low tide was another matter and I really learned a bit more respect for the Arun after being thrown around and under Pulborough Bridge before managing to beach and unload!

The second test, two days later with bolted mounting bar, was on the Thames with the prop lowered at different levels through the day and to see just how long a single charge would last. (Manual states the Bison 62Lb drawing 58A at full load) After a full day of trolling about mainly at about motor level two of five, the battery finally gave out, of course just as I was passing above a weir!

I think it important to note that if inspecting or relying on the Bison motor’s battery gauge, stopping the motor to kneel up in the kayak and view the gauge results in the gauge registering more than the battery has remaining. In therefore stopping and checking the gauge which still registered at 5/10 remaining, once under load, this changed to 1/10. I’m therefore adding my small 12v battery tester to my essentials kit now.

I reckon I managed to get about six hours of motor use out of that battery all told, so would work to a max of about five to avoid the really low battery level that I hit. I really wasn’t rushing about and only used level three  or above to fight the current or wind at times but still feel very impressed and much more confident to look at longer excursions with the motor as a backup to get me back or out of tidal misfortunes/miscalculations.

With the higher power of the 62Lb motor, I wouldn’t recommend using level five with a fully charged battery on the kayak. The strain on the mount is greatly increased as the gearing seems to change dramatically between levels four and five, resulting in a massive surge of power. The stability of the kayak also then changes and increases the danger of accidents. My intention to use this motor on another small dinghy is the only reason I went up to that size and I’d certainly recommend going a degree lower to save on motor weight and battery life.

Conclusion

For the aims I set out with, I feel I have achieved what I required. I can fairly easily load, unload, launch and land the kayak in various conditions with the full motor kit, paddles and a couple of backpacks of supplies and sundries. I could even, at a pinch, transport the whole kit on a train should I end up a great deal further than I expect! Certainly makes a lot more bother than just loading up the kayak, pump and paddle but for longer excursions and lazy days it is ideal.

How about cost? Well, the only things you need to make the motor mount are the wood, chin-up bar, two bolts, four bungees and some foam. £20-40 depending on the wood. Spurs me on to make outriggers for less than the £200+ price tag I’ve seen for some!

I’ll write an update with final photos when I complete the project and as ever, on looking at my work so far have thought of possible improvements. I am wondering if turning the bars the other way up could make a mount that includes the outrigger fittings if only on one side of the kayak.

Link to second installment