Transom mount for long (L) 20″ shaft outboard motors – W500 Series

Wavewalk® TMM 20-A Transom Motor Mount for 20″ Long (L) Shaft Outboard Motors

This Mount is For The 500 Series Only

IMPORTANT: We recommend using 20″ (long) shaft motors, since they can be mounted at the rear end of the cockpit, and not a few inches behind it. When the motor is closer to you, it’s easier for you to start it and access its controls, and it makes steering easier. Only 20″ long (L) outboard motors fit outboard manufacturers’ requirements for the depth of the anti-ventilation plate below the boat’s lowest point. Do not use 15″ short (S) outboard motors with this motor mount.


  • Price:  $160.
  • Shipping:

No extra charge when shipped together with a Wavewalk® 500 kayak.

We do not ship this item separately.


Materials and Construction

The TMM 20-A is made from 3/4″ thick Medium Density Overlay (MDO), a composite wood and polymer resin (a.k.a. plastic) material developed for outdoor use such as signs and marine applications.  The front and back of the MDO panels come coated with a waterproof polymer-infused layer, and the sides of the parts that form the TMM 20-A are waterproofed with polyurethane. Unlike the TMM 20 motor mounts that’s  made from Trex, which is a heavier material, the MDO used in the construction of the TMM 20-A makes it considerably lighter.

The parts from which the TMM 20-A is made are cut with a computerized router for maximal precision, best fit, and optimal strength. They are assembled and glued together with waterproof adhesive. The tab-and-slot technique and ‘caisson’ design applied in this product give it additional strength.

There is no need to paint this motor mount, but in case you want to, it can be painted with special paint for outdoor plastic, such as Krylon Fusion spray paint. Regular paint doesn’t adhere well to its surface.

The bolts, washers and nuts used in this motor mount are made from zinc plated steel.

Dimensions and Technical Specifications

  • Width:  21.5″ (54.5 cm)
  • Height:  5″ (12.7 cm)
  • Depth:  6.5″ (16.5 cm)
  • Weight:  2.5 lbs (1.14 kg)
  • Horsepower Compliance:   This motor mount was tested with small outboard gas motors such as commonly used with Wavewalk® 500 kayaks.  We do not recommended to use it with motors stronger than 3 hp. In case you have a more powerful motor and you want to use it with this motor mount,  you’d have to reinforce its mounting plate or get a TMM Heavy Duty (HD) 700 motor mount. Failing to do so is hazardous, and could result in serious accidents.

How to attach this motor mount to your Wavewalk® 500 kayak

Place the mount as close as possible to the rear end of the cockpit, as seen in the picture below, make sure it is centered, mark the two spots where you’d need to drill 3/8″ holes for the blots, and drill.


TMM 20-A Transom Motor Mount

Bolt the motor mount in its place by tightening the nut knobs with their Tee nuts facing down.

You can secure the mount in place with an extra pair of 5/16″ nuts. Doing so could reduce unwanted vibrations resulting from the wooden knobs getting loose.


More about motorizing your kayak »

Safety and Operation


Before going on a motorized trip, verify that the wide wooden bolt knobs that secure the motor mount to the boat are safely tightened to the maximum. Failing to tighten the bolt knobs could result in unwanted vibrations and noise. If you feel such unusual vibrations and/or hear unusual noise, stop the motor, turn around, and tighten the bolt knobs to the max.
Driving with loose bolt knobs is hazardous, similarly to driving with the motor’s clamp screws loose, and it could result in an accident.

Never operate the motor without the motor’s stop switch (“kill-switch”) attached to your arm.

For motor operation and maintenance please refer to the motor’s owner’s manual.


  1. PackerYaker

    Looks great, Yoav………..and only 2.5 lbs. Looks like it should weigh considerably more.

  2. fish kayak

    Thanks Gary,
    Yes, MDO is a much lighter material than Trex, since Trex is very dense. The MDO gets its strength from the overlay structure of the wood fiber.


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