How much HP for my S4 skiff’s outboard motor?

This article summarizes research performed by Captain Larry Jarboe, as well as inputs from Wavewalk dealers and S4 clients. Its purpose is to answer a frequently asked question (FAQ) from prospecting clients, which is “What outboard motor should I choose for my S4?”

The answer is that the outboard motor you should choose for your S4 depends on two factors, which are

  1. How much power you need
  2. How important is the motor’s weight for you

And there is a trade-off between power and weight, namely that the more powerful the motor, the heavier it is, and the harder it could be to carry it.
In any case, the motor should be a 20″ log shaft (L) model, and not a 15″ short shaft (S) model.

2 HP outboards

Outboard motors in this class weigh around 30 lbs, which makes them fully portable even for a user who’s not very strong. A 2 HP motor can propel an S4 skiff with one person on board at speeds up 8 mph, even in choppy water. This speed would decrease as the boat is required to carry more passengers on board. S4 owners who tested such motors with their S4 skiff reported that the boat felt under powered, which means that they felt like going faster, but the motor lacked the powered required for this. For this reason 2 HP motors are not popular with S4 users. Another reason for their lack of popularity is the fact that being air cooled makes them noisier than water cooled motors.

3.5 HP outboards

Outboard motors in this class weigh around 40 lbs, which makes them still portable, but less so than 2 HP motors. A 3.5 HP motor can propel an S4 skiff with one person on board at speeds up 14 mph, even in choppy water, and it can propel the boat at 12 mph with three passengers on board in  moving water. This size motor is the most popular among S4 and W700 users, as it offers a good trade-off between power and weight for people who must lift the motor or carry it by hand over long distances.These motors are also less expensive than bigger ones.

6 HP outboards

Outboard motors in this class weigh around 60 lbs, which makes them portable only for very short distances, and not for everyone. A 6 HP motor can propel an S4 skiff with one person on board at speeds up 18 mph, and it can propel the boat at 14 mph with three passengers on board. 6 HP motors are the second most popular motors among S4 users.

8 HP outboards

Outboard motors in this class weigh around 80 lbs. At such weight, these motors can no longer be considered as portable, and the only reason to use them is the fact that they are offered with electric ignition, which eliminates the need to start them by pulling a cord. The S4 outfitted with an 8 HP motor performs well in choppy water, but it could feel over powered for an inexperienced driver, which should avoid using such motors with their S4. Heavy users may benefit from driving with a U-jointed tiller extension, in order to move some weight forward from the stern to the middle of the boat.

6.5 HP mud motors

Mud motors are bulkier and heavier than regular outboard motors. A 6.5 HP mud motor weighs around 80 lbs, and it’s not portable. The reasons you’d want to use such a motor instead of a regular outboard of similar power are if you need to go in very shallow water (skinny water) and mud, and if you fish or hunt in water with plenty of vegetation and underwater obstacles. The S4 performs very well with a such a mud motor. We do not recommend using less powerful mud motors because typically, these motors require more power than regular outboard motors do.

Electric outboard motors

Some electric trolling motors are described by their manufacturer as “outboard motors”, namely comparable in power to small outboard gas engines. If you consider such electric motors, we recommend remembering the laws of physics, and applying the formulae for Kilowatts to Horsepower conversion, which are:

  • 1 KW = 1.34 HP
  • 1 HP = 0.745 KW

 

 

 

 

 

 

6 Comments

  1. Bassman

    Yoav et al.

    In view of the Wavewalk transition to portable motorized twin hull skiffs (the S4 series), I have been finding and refurbishing small long shaft outboards for my customers to compare.

    No other kayak dealer that I know of will demo their product with a motor capable of planing the vessel.

    I also offer these motors for sale at less than half the price of a new long shaft outboard.

    In case anyone needed another reason to visit Key Largo…

    Larry J.

  2. fish (Post author)

    Larry,

    I’m sure your clients appreciate this service.

    Yoav

  3. Pyt Rotary

    Good information.
    I just tested 2Hp Honda and indeed there is room for more power.
    Will get a 6Hp next year.
    Have fun and be safe.
    Canada.

  4. fish (Post author)

    Thanks Pyt,

    Yesterday I drove the S4 with the 6 HP Tohatsu at full throttle at the beach.
    BTW, this motor’s user manual states that it can propel boats up to 3,000 lbs. I guess this means a sailboat maneuvering in a harbor.
    Anyways, driving was a lot of fun, both sitting and standing, and playing with waves and other boats’ wakes. I drove at full throttle all the time, including while turning.
    And this is where I need to make it clear that I’m not exactly and experienced driver.

    Following this fully positive experience, I let my older son drive the boat, although he had never driven a boat before. He went full throttle too, seated and standing, while shooting videos and pictures of himself, to show his friends 🙂

    Therefore, I am modifying our recommendations for the S4 to include 8 HP motors for experienced drivers, and I’m willing to accept the notion that very good drivers may use bigger motors – at their own risk of course 😀

    Pulling the 6 HP motor from the car and mounting it on the boat was OK, but I would have not made it with a heavier engine.

    Yoav

  5. Bassman

    My own opinion is that the S4 will easily accommodate as much motor as your back will. Thus, choose the most horsepower that you can sensibly lift.

    I look forward to enjoying my day seated inside my Wavewalk not lying on top of a chiropractor’s table.

    Been there. Done that. Will look out for my back to avoid going back.

    Larry J.

  6. fish (Post author)

    Yep, this is good rule of thumb.

    Yoav

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