W570 with a 6 hp Tohatsu outboard motor

Why overpower this fishing kayak with a 6 hp outboard motor?

Earlier this year, Kenny One-Shot Tracy outfitted his W500 kayak with side flotation and a 6 hp Tohatsu outboard motor, and showed it going at 13 mph. This was intriguing, and several months later, after we came up with the W570 series for offshore fishing, we wanted to test it with a similar motor.
A W kayak weigh 60 lbs and it’s rated for 2-3 hp motors, so it goes without saying that using it with a 6 hp motor means overpowering it, since these motors are rated for moving boats up to 3,000 lbs, that is 50 times heavier.
However, testing and experimenting are part of any Research and Development (R&D) process, and we try as much as we can to test our products under various conditions in order to better understand possibilities, problems, and hazards, and inform our clients about them, so they have more options to choose from, and can make better decisions.

Tohatsu America showed interested in this project and cooperated with us through their dealer Steve’s Marine in Rhode Island, and we got the 6 hp Tohatsu motor (20″ shaft) in late October.

beached motorized kayak

Wavewalk 570 beached.

 

Driving-a-motorized-fishing-kayak-640

 

Watch the movie –

Motor weight and handling considerations

Although the 6 hp (20″ long shaft) Tohatsu is a sophisticated outboard motor, it is relatively lightweight for its class. However, at 59 lbs it still weighs twice more than the 2-2.3 hp Honda outboard that we’ve routinely used so far.  This additional weight was our first concern, and we wanted to experience what it means for a W kayak angler who uses such a motor.
We found the weight difference to be noticeable, but not a major issue – It’s possible to carry such a motor over short distances, whether on its own or mounted on the kayak. Dragging the kayak on a sandy beach was considerably more difficult, but not a big problem over a short distance.
Lifting the motor into the car wasn’t too hard either.

Transporting the boat in the car

Click images to enlarge –

 

The boat on the beach and at the dock

Launching is easy both from the beach and from a dock, and the same is true for beaching.

Click images to enlarge –

The motor mount

Kenny reported that his 6 hp Tohatsu outboard had broken a DIY motor mount. Such accidents can be dangerous, so we knew that we had to consider both weight and power. Kenny later reported that his 6 hp motor worked with the TMM 20 motor mount that we had sent him, but we preferred to beef up a TMM 20-15 motor mount with an additional 3/4″ board for its vertical mounting plate, making it 1.5″ thick.

The boat itself

Another concern we had about the 6 hp motor’s weight was how our W570 would take it.
The following pictures show that we had no reason to be concerned, as the boat is pretty much level, and the side flotation modules rest several inches above waterline –

motorized fishing kayak

motorized fishing kayak

Rear view of a docked Wavewalk 570 INF 20-15 outfitted with both a spray shield and cockpit cover, and an extra inflatable flotation module attached between its hulls.

Driving the boat

Driving the boat with the 6 hp Tohatsu / 20″ shaft was easy and convenient.
This outboard motor features a 3 position gear system (Forward-Neutral-Reverse) that’s safer than a centrifugal clutch, and makes it easy to start any time. The fact that this motor is water cooled makes it relatively quiet in comparison with the air cooled 2-2.3 hp Honda.
Access to the motor’s controls is easy and convenient once you slide backward on the saddle all the way to the back of the cockpit.
The inflatable flotation modules stayed above waterline and did not cause splashing.

Load and additional passengers

Although a W kayak can carry heavier loads, we rate these kayaks for a total load of 360 lbs, for both safety and performance reasons. This number includes everything that the boat may carry, from passengers and their personal belongings to fishing gear, an anchor, and last but not least – a motor. With a 60 lbs motor and all the extra accessories that come with the Wavewalk 570, and considering the high speed in which you’re likely to drive, it would be safer to consider the W570 as a one-person motorized kayak, or a solo skiff, if you prefer. This is unless the user is not heavy, and they take a lightweight passenger on board. For example: A driver that weighs less than 200 lbs could take on board a small child weighing 60 lbs, plus some lightweight fishing tackle.

Fuel consumption

The 6 hp Tohatsu outboard model that we’ve tested features an integral fuel tank that allows it to go for 45 minutes full throttle, but as long as you drive a W570 with it you won’t go over 1/3 throttle since doing so is likely to increase your speed dangerously, unless you’re towing a bigger boat or several kayaks and canoes.

Accident

In one occasion, while the boat was going pretty fast, the propeller hit a rock on the bottom of the lake, and got ejected out of the water, as it’s designed to do in such cases. Lowering it back into the water presented no problem. The reinforced TMM 20-15 transom mount didn’t budge, and the inflatable side flotation proved that it’s useful in helping to prevent the boat from rolling (flipping) if it’s tilting strongly as it did following the impact and momentary loss of control that resulted from it.
The role that the inflatable flotation played in that accident emphasizes its importance.

Power and speed

A W kayak outfitted with a 2-2.3 hp outboard can go at 8.5 mph, full throttle, while the same kayak outfitted with a 6 hp Tohatsu motor can reach 13 mph at 1/3 throttle, a speed that for most people makes it too much of a challenge to drive safely. This is where we found that a 6 hp motor wasn’t the best fit for the Wavewalk 570. In other words, overpowering the W570 with such a powerful motor can be hazardous and cause accidents if you drive too fast relatively to your boating skills and/or to water conditions, or if you accidentally accelerate abruptly or even just too quickly for you to safely maintain control over the vessel.
This lightweight craft is no match for the power and torque of such a big engine, and that makes it too ‘nervous’ compared to when it’s outfitted with a smaller and less powerful motor that tks longer to accelerate.

Why you might want to overpower

Having said that, you might like this overpowered configuration if you’re a risk-loving speed fan who enjoys the feeling of danger. It’s your choice, as long as you’re aware of the safety hazards, and you know that the W570 isn’t rated for motors that are more powerful than 2-3 hp.

A more productive way to make use of such a disproportionally powerful motor could be for towing other boats. For example, if you use the W570 as tender (auxiliary service boat) for a bigger leisure craft such as a sailboat, it could tow the mother ship, if necessary, or tow another tender with several passengers and provisions on board (e.g. an inflatable dinghy).
If indeed you’re thinking about such use, make sure the towed craft are properly attached to your W570, and don’t use its handles or eyelets for this purpose.
Similarly, if you go on a camping and fishing trip in which several people take part, your W570 on steroids could tow several kayaks and canoes over long distances, and make life easier for the other members of your expedition.

If you’re thinking about driving up fast rivers, such as in springtime, or on fast tidal rivers, more power and torque may be justified, although it’s hard to imagine cases where a 2-3 hp motor would not suffice for your W kayak. Just remember that fast moving rivers are hazardous, and we recommend neither paddling nor motorizing in them.

Another case in which you could be interested to use a 6 hp outboard motor with your W570 is if you already own a larger boat that you propel with such a motor, and you want to alternate between your W570 and that bigger boat. For example, you may prefer to go fishing on your own in the W570, and take the bigger boat when you fish with your family and friends. If you don’t like to purchase a smaller outboard for your W570, you could try using your 6 hp outboard with it, and see how it works for you. If it does, it could save you the additional expense on a small motor. Just remember to be very cautious with the throttle when the motor is mounted on your W570.

Rating

All the above said does not imply that we rate the W570 for use with an outboard motor that’s more powerful than 2-3 hp, because we don’t. We think that using a W kayak with motors that are more powerful than 2-3 hp could be hazardous.
Again, the purpose of this article is to inform people about what using much stronger motors implies, and warn them about problems and dangers associated with such practice.

More reading

Motorized kayaks »

Driving the W570 in the ocean »

The New Wavewalk 570 Series (W570) 2015 Models »

28 Comments

  1. Chris Henderson

    You look like you are having too much fun with this test. I think you might be secretly hoping someone puts a 4 cylinder inboard in one so you can test that too. Lol.

    Knowing a boats limits and stepping back a bit from those for safety is always a good idea. Thanks for testing it out.

  2. fish kayak

    Thanks Chris,

    I wish I was 20 years younger and the temperature 20 degrees higher for playing with this awesome toy! 😀

    Yoav

  3. One-Shot

    Great article and video Yoav! I can’t wait to finish my current project, because my next “W” may INDEED be the recipient of a 4-cylinder motor I just happen to have sitting around…. Hmmmm. Has anyone ever seen a micro-skiff (or any other boat for that matter) with a 6-speed transmision?!? IJS

  4. fish kayak

    Thanks Kenny,

    Hey, now you got me really worried! 😀

    Yoav

  5. fish kayak

    Just to put this article and discussion in perspective, it may interesting to see what this information means in terms of electric trolling motors –

    Peter is a Canadian client who’s been fishing out of his W500 for over 5 years. He gradually transitioned from paddling to powering his kayak with electric motors, and here’s what he wrote me: –
    “I am very happy with my 70Lb(24V) thrust Minnkota that run fine on a 12Kg AGM (two 6Kg batteries). At full throttle in no wind I get 10+km/h. For big lakes I use 70Lb for small lakes 40Lb.”

    10 km/h is 6.2 mph, and 6 kg is 13.2 lbs. A 70 lbs electric motor weighs about 20 lbs.

    Peter added: -“One plus for having and electric motor and not gas is that the kayak becomes more stable having the center of gravity lower.”
    By this he means that he stores the batteries at the bottom of the W kayak’s hulls, so they rest below waterline and thus don’t add instability. In contrast, most of a gas outboard motor’s weight is concentrated above the kayak’s deck, which is a destabilizing factor.

    As far as weight is concerned, (2 x 13 lbs) + 20 lbs = 46 lbs, which is 1/2 more than the 2 hp air-cooled gas outboard motor that we normally use, and about 1/4 less than the weight of the 6 hp Tohatsu outboard that we tested for this article and video.
    In terms of power and speed, 6 mph is pretty good, but it’s hardly enough when the wind blows in your face and the lake gets choppy.

  6. danko

    This article got me a little confused… The first paragraph talks about overpowering but the video looks good and there’s no apparent problem, and there’s so much information to digest.. So what’s the bottom line, what’s the biggest problem with this 6HP setup? Is it stability? safety? power? or maybe I missed something?..

  7. fish kayak

    Torque is the main problem that we see at this point – The extreme power to weight ratio in this configuration is almost absurd, and this makes this craft very ‘nervous’. Every little twist of your wrist can instantly deliver a huge spike in RPM – It may not be such a big increase in absolute terms, but because its impact on the boat is so strong it feels like it could make you lose control. You almost feel like it’s jumping.
    The closest thing that’s comparable is riding a very strong but untamed horse* – you know that you just can’t afford to make a mistake.

    Having said that, it’s possible that practicing driving this wild beast would make things better. In principle, it should, since practice makes perfect 🙂
    Once the weather gets warm again, next year, we’ll try to spend more time driving it.
    BTW, getting used to the 2 hp motor took a short learning curve, but this time it’s a different animal, and it seems like results may vary…

    Yoav

    * I actually had such an experience, many years ago. It was pretty tough! 🙂

  8. Pete

    Playing with the motor’s throttle friction adjustment screw could help reduce the likelihood of accidentally turning the throttle too quickly in the wrong direction.
    Pete

  9. fish kayak

    True, but over-tightening can be dangerous as well, since it might lead to loss of control if the driver can’t reduce power fast enough in case of an emergency.
    In the end, it’s much about getting used to driving this thing through a lot of practice.

  10. 1formidable

    I’m thinking about a 3.5 Tohatsu with a 20 inch shaft. Could you show how you reinforced the 2015 transom mount?

  11. fish kayak

    We just attached a 3/4″ plate in front of the mount, and relocated it 3/4″ backward:

    reinforced motor mount for fishing kayak

    A motor featuring a 15″ (short) shaft cannot be mounted directly behind the cockpit because of the need for enough room for the clamp screws that attach it to the mounting plate.
    Outboard motors that are over the 2-3 hp range should feature only a 20″ long shaft.
    This is because of their higher weight, and because they must be close to the user in order to be accessible and easy to steer. This is important both for convenience and safety.

  12. One-Shot

    Hey guys,
    I think Yoav’s statement about “Practice makes Perfect” truly says it all. The 6-HP motor turns your micro-skiff into a “specialized vehicle” the requires a skillset that “beginners” simply don’t possess. However, if your reasons for having the powerful powerplant are necessary for what you want to use it for, go for it… Just be careful. I wanted a micro-skiff (small boat I could transport in my pickup bed) that I could run lights, radios, and other accessories that I can use for comfortable (safe) night fishing in a bay that oftentimes gets rough (white-caps/big waves/high winds) really quickly. The 6-HP (sail-pro) was the smallest motor I found that had an alternator already built in. In my case, I am basically building a customized boat “around” the W500’s GREAT “bones/frame/platform” to suit MY particular needs, even though it was an incredibly capable fishing kayak when I first picked it up.

    Go WaveWalk!!! Whoo Hoooo!

  13. fish kayak

    Kenny,

    Thank for reminding us about the alternator – This is a feature that some people may be interested to know more about. It’s a standard feature in the Sail-Pro models, but you can add it to the other 6 hp Tohatsu models as well.
    What it does is enable you to recharge a battery on board. You can use the battery to power a small trolling motor, lights, etc.
    Since the 6 hp Tohatsu features a 3 position gear, you can run the motor on idle, and charge whatever electric device you have on board. It’s pretty cool, although not cheap.

    Yoav

  14. PackerYaker

    OK, when and where is the race between Yoav and One-Shot. My money is on One-Shot.

  15. fish kayak

    Gary,
    Kenny is a motorcyclist and I’m not, so I have no chance racing against him. That’s what he meant by “skill set” 🙂
    Yoav

  16. macreel

    is this a w mokai?
    –steve

  17. fish kayak

    Steve,

    I have never driven a Mokai, and all I know about it are things that a couple Wavewalk clients who had owned such a boat in the past have told me (they liked it), and what I was able to learn through watching online videos and reading tech specs.
    The Mokai has been around for many years, and the W570 overpowered by a 6 hp outboard is a concept that’s still at an experimental stage.
    I don’t think your question is misplaced, but I at this stage my answer could be 🙂

    Yoav

  18. Fish Wiz

    Are they fishermen?
    FW

  19. fish kayak

    Yes. The first was Andy Kumler, a fly fisherman from Oregon, who used his Mokai for going in fast rivers, on his way to fish trout, salmon, etc. He later got a W300, and contributed a review and a video to our website. The second is Steve Lucas, from southeastern Florida, who used his Mokai for fishing trips in the everglades and the flats in his area. Steve recently contributed a great review of his W500, and some nice movies. He had plans to motorize his W500, but he still hasn’t done so, as far as I know.

    Yoav

  20. macreel

    the great thing about the mokai is its jet drive
    it’s great for shallow water and you should develop a jet drive too. it would fit perfectly between the w pontoons
    –steve

  21. fish kayak

    Generally, jet drives work better in very shallow water (‘skinny’ water) than outboard motors do, but we won’t develop a jet drive because we don’t think that the average user has the technical skills required to maintain and repair such specialized motors.
    The unbeatable advantage that outboards offer is that you can easily find a local dealer or mechanic shop that would take care of your motor if you live anywhere in the US and Canada. It’s the most convenient solution.
    Besides, cleaning an outboard’s propeller from weed is easy, and so is replacing it. In general, outboard maintenance is the easiest.
    The second advantage that outboard motors have in this case is that they’re less heavy than comparable jet drives. A motorized W is a lightweight car-top boat, and we’d rather keep it as lightweight as possible.
    BTW, the 6 hp Tohatsu outboard features a shallow water position for its propeller. We haven’t yet had the time to test it, but it’s worth mentioning in this context.
    The third advantage of outboard motors is their low price compared to jet drives. The total expense for a W500 or W570 outfitted with an outboard motor is between $2,500 and $3,500 including shipping in the continental US, but a W featuring a jet drive would cost over $5,000, which is expensive for a little fishing boat 🙂

    Yoav

    PS — The W features twin Hulls used for carrying passengers and gear. A pontoon is a closed buoyant structure that isn’t used for carrying passengers or cargo.

  22. PaulZ

    MacReel, there are special outboard motors for rocky rivers, shallow water and mud.They’re called mud motors or backwater motors, and they weigh just a little more than outboards in the same power range without being much more expensive. You can mount them on any small boat, and I bet you could do it on a WaveWalk too.

  23. Pete

    I wouldn’t be so sure mainly because those mud motors are designed for wider boats with a square stern and a driver standing up. It might be possible to mount such a thing on a w if the steering frame is modified. I’m thinking that it may be easier and cheaper to outfit the propeller of a regular outboard with the kind of sturdy protection fins and collar that mud motor propellers feature, and drive in the “shallow water” position. It might not be a perfect solution like a jet drive or a mud motor, but at least it would be more versatile and practical.
    Pete

  24. fish kayak

    Interesting idea!

  25. lake

    The next thing you should do to this fishing kayak is turn it into a snowmobile…

  26. fish kayak

    Indeed, maybe we should 🙂

  27. lake

    I hear that jet drives can get clogged by debris in shallow water. I thought you’d like to know that.

  28. fish kayak

    It makes sense.

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