Outboard motor propeller shaft length for Wavewalk fishing kayaks and boats

November 12, 2016

Wavewalk will no longer support the installation of any outboard motor whose propeller shaft is shorter than the standard 20″ long (L) on its W500 fishing kayaks and W700 portable boats.

How to measure an outboard motor shaft’s length?

An outboard motor’s propeller’s shaft length is measured from the top inner side of the motor’s clamp bracket to the horizontal anti-ventilation plate located above its propeller. Read more about how to measure this length precisely »

The outboard motor industry has determined four standard lengths for outboard motor shafts, which are:

  1. 15″ (S) “Short”
  2. 20″ (L) “Long”
  3. 25″ (XL) Extra Long
  4. 30″ (XXL) Extra Extra Long

For both the Wavewalk 500, 700 and 4 series, the length we recommend is 20″ (L).

What’s wrong with short shaft outboard motors?

Depending on the type and quality of the motor mount’s installation, the use of shorter shaft motor (electric or gas) can result in any of the following problems:

  1. Motor mount’s mounting plate too high – Strong vibrations and loss of power due to ventilation that occurs when the propeller rotates at high speed too close to the surface, and its top part goes through a mixture of water and air bubbles coming from the surface.
  2. Motor mount’s mounting plate is too low – The motor mount’s mounting plate’s lower side scoops water and generates excessive spray, some of which can find its way to the back of the cockpit, and some to the top part of the motor.
  3. Motor mount too far behind the cockpit – Access to the motor’s controls is not easy, including for starting it, shifting gears, using the choke button, and refilling gas. Driving is harder too. The driver is forced to drive from the cockpits rear end, instead of driving from the middle of the cockpit.
  4. Motor mount’s mounting plate too low, and mounting plate too close to the cockpit – The motor’s top part is prevented from tilting downward in case the lower part of the propeller hits bottom or a submerged object and gets pushed upward automatically, in order to avoid damage. If this basic safety function is disabled, the propeller is exposed to severe damage, and so is the propeller shaft.

For the above stated reasons, Wavewalk does not recommend using any motor, electric or gas powered, whose propeller shaft is shorter than the 20″ (L) standard length.

Why does Wavewalk restrict its support now?

In the past, Wavewalk supported owners’ efforts to outfit their W500 kayaks with short-shaft motors. This policy stemmed from the fact that long-shaft motors in the 2-3 HP range are harder to find than short shaft ones, and we don’t recommend more powerful motors for the W500 series.
Installations of short shaft motors on Wavewalk kayaks and boats worked, but they were sub-optimal, since there is practically no way for a 15″ setup to match the performance and convenience that a 20″ outboard offers when properly mounted on a Wavewalk.

Last year we came out with the W700 series that’s compatible with several 20″ (L) outboard motors up to 6 HP, which is to say that since then, Wavewalk owners benefit from a much wider choice of outboard motor models.

Currently, the only outboard motor under 3 HP that we recommend is the lightweight, air-cooled 2.3 HP 20″ (L) 4-Cycle Honda.
Several outboard brands offer water-cooled, long shaft (L) motors in the 3.5-6 HP range, and our preference goes to Tohatsu, since these outboards (also sold under the Mercury brand) feature a gear shift lever in the front side of the motor, where it faces the user, which makes them easier to use.
Other 20″ (L) quality portable motors in the 3.5-6 HP range are offered by Yamaha, Honda, Suzuki, Evinrude (6HP only), etc.

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