Driving an S4 motorized kayak skiff with a 9.8 HP Tohatsu outboard at 17 mph

Captain Larry Jarboe from Wavewalk Adventures in Key Largo, Florida, drives his “White Knight” workhorse S4 kayak-skiff powered by a 9.8 HP 2-cycle Tohatsu outboard motor, outfitted with a 9″ pitch propeller.
Larry easily gets to a 17 mph speed, which is probably a world record for vessels that are officially designated as kayaks, such as the S4.
He drives sitting in the side-saddle position, similarly to the way that he’s been driving dinghies and other small boats for decades – No stability problems, and no control problems, even in the chop. Most people who drive the S4 and other Wavewalk kayaks / boats do it in the riding position, with a leg on each side of the saddle seat, similarly to the way that Personal Watercraft (PWC a.k.a. jet-ski) drivers operate these vessels.

Generally, 2-stroke outboard motors are lighter than comparable 4-stroke outboards, which makes them more portable.
9″ is the highest pitch for propellers that fit this motor. A propeller with a higher pitch would have probably added some speed to Larry’s record. In any case, 17 mph falls within the upper range of speeds achieved by small, lightweight boats with propellers of such pitch.

 

Practically speaking, this performance coupled with the S4’s capability to carry on board up to three anglers and their fishing gear, puts it on par with Jon boats, skiffs, and even some bass boats.
The S4 is an ultralight car-top boat that can be launched and carried anywhere, as well as paddled in extremely shallow water, and it is most seaworthy. These facts offer its users an advantage that neither conventional nor new boats do.

Note that Larry is a most experience boat driver, and driving such a small craft at such high speeds requires skills that not anyone has. This is to say that we do not recommend such powerful motors for the S4.

6 thoughts on “Driving an S4 motorized kayak skiff with a 9.8 HP Tohatsu outboard at 17 mph”

  1. Outstanding!

    That 9.8 hp outboard motor really makes the S4 fly.

    And yes, everyone who watches this should remember, Captain Larry has
    the experience to handle that S4 or any vessel at it’s top speed.

    I can see that Captain Larry’s guide service is going to rocket this year
    with his Wavewalk Kayaks, his guide service through the Mangroves should
    be one of the Hottest service in the Keys.

    I hope to meet Captain Larry some day, even go for a trip through
    the mangroves if time allows me in April when we go down to
    Clearwater Beach. 🙂

    Tight Lines and MoPaddle Safe All.
    Rox

  2. Rox,

    Even locals enjoy going with Larry on his Wavewalk fishing trips, and the restaurant next door cooks the fish that he and his clients catch 🙂
    It’s non-stop fun!

    Yoav

  3. Update – July 2019

    Larry recently tested the S4 with a 25 HP 2-stroke Johnson Outboard weighing 110 lbs.
    At around 20 mph, he noticed that the only contact the boat had with the water was through its propeller. In other words, the hull was planing so much that it was almost completely out of the water, a situation that’s potentially hazardous, due to deficiency in control, namely no way to steer properly.
    So Larry had to slow down.
    Ironically, the S4’s light weight and the flat surfaces of its twin hulls limit its top speed when no extra accessories are used to increase contact with the water.

    Yoav

  4. Yoav & All,

    After experimenting with the higher hp outboards, I can reaffirm that long shaft outboards in 3.5 – 6 hp range are ideal for the S4s without modification to the transom.

    Enough said.

    Larry J.

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