Top 5 tips for adding an electric motor to a kayak

'Yak fishers love their little watercraft, and can often reach places to target fish species that are ordinarily way out of bounds for either land- or boat-based anglers.

There are also a number of restrictions being lifted on a number of impounds across the state, opening up waterways that have not been fished in decades, but with the caveat that only vessels using electric propulsion can launch on them.

But how do you decide what battery-fuelled system is right for your kayak? Here’s the boatsales.com.au guide to working out what is the best combination for you.

There are two considerations at play here: how much power your electric motor draws, expressed as amp hours, and how big a battery you’re going to need to get where you need to, and back again.

The general rule of thumb is an electric motor producing a single pound of thrust will draw about one amp an hour. Most battery-powered watercraft exemptions allow electric motors up to 40 pounds of thrust, which is equivalent of 40 amps an hour.

On paper, a deep-cycle 12-volt battery with 35 amp hours will theoretically survive a little over 50 minutes of running – the equivalent of around 4.0 nautical miles of range.

But there’s a catch. Generally speaking, you’re not going to run a deep-cycle battery to dead flat, and in a worst-case scenario, you’d only reduce it to 50 per cent of charge. So real-world running time and range are around 25 minutes and 2.0 nautical miles, at best.

There’s the weight issue, too, because a 35Ah battery tips the scales at around 17kg of dead mass. Reducing the number of amp hours – and therefore run time and range – a battery stumps up can go some way to fixing this.

Don’t use a car battery. They are made for pumping out a lot of energy quickly, while the kayak’s motor will need the slow and steady power delivery of a deep-cycle battery.

The most obvious consideration here is whether you’re fishing in saltwater or freshwater.

An electric motor made for saltwater fishing will handle the trials of pushing you through freshwater just fine, but the harsher saltwater environment won’t be kind to a system not built to handle the high salt concentration of seawater.

You’re also going to have to think about how you’re going to steer and operate your electric motor. Products on offer range from those with enough smarts to even act just like a virtual anchor to those more simple ones with just two speeds – full ahead and stop.

Importantly, whatever the system, ensure the electric motor is fitted with a kill switch. If you happen to fall out, it’s much better that the kayak recognises you’ve gone for a swim than to just motor on into the distance without you.

Somehow you’re going to need to mate the electric motor with the kayak. There’s a lot to consider in this.

The main issue is where you’re going to mount it. We’ve already established that unless you like lugging big batteries around, you’re going to have to paddle for at least some part of the time you’re out on the water.

This means you’re going to need to tilt the electric motor up out of the water.

That rules out mounting it directly behind you so that you can reach the electric tiller.

A kayak mount can add significant weight to a kayak, and if you have all that extra weight sitting to one side, counterbalancing it will be an important part of tuning the build.

Mounting will also often mean drilling a hole in your kayak. A general rule of thumb for drilling a hole in any boat hull is to think about it, think again, and then don’t do it, but on a smaller hull this is often not an option.

Stick to professionally built brackets made specifically for mounting electric motors on a kayak so you know they will work.

All up, you could be adding around 25kg to a kayak by the time the electric motor is mounted and ready to go. That’s not including iceboxes, fishing rods, nets safety gear, lunch and a bevvie or two to keep the hydration up.

That’s a lot of weight on top of the kilos you’ll be adding once your arse falls into the seat.

Ensure that your kayak can still float and perform with the extra weight on board. Consider adding flotation foam inside the hull so that if things do go bad – say a mounting screw pulls out so the hull is breached – the hull will still have positive flotation.

Think about what will happen if you come off the kayak and it capsizes. Keeping the heavy battery as low as you can in the boat makes it easier to right if it is inverted, not to mention make the upright kayak more stable under human or battery power.

The most obvious thing to do when fitting any sort of electrical system to a boat is to ensure you have fitted a fuse that will protect all the sensitive electronics. There’s no point in frying the fish finder that one time a rogue wave crashes across the bow and shorts out the battery.

If you’re spending big money on a battery with the performance you need, don’t cheap out on a battery charger. Buy the best you can to ensure the battery is in tip-top condition, and always whack it on the charger as soon as you get home – don’t wait a day or two.

A battery monitor will give you an idea about how long your energy use will last. This is particularly important under changing conditions when the wind swings around to a brisk northerly and you have a short, sharp half-meter swell to punch through on the way back across the lake.

It will also help you manage fatigue as you share the of getting back ashore with the electric motor.

Adding a zinc anode to the electric motor will help protect it against a boatie’s nemesis: electrolysis.