We decided we would add Transom Motor Mounts to our kayaks.

Here is a bit of a build guide on the one made for Jack’s Ocean Prowler Big Game II.

The big game II has been re-homed, So ill do the best I can to describe and use pictures and videos we took when we made it.

Motor rigger ready to hit the water


To start, We needed to find a way of getting access to the inside of the BGII right at the rear.

This is, so we could get access to put oversized washers and Nyloc Nuts on the Bolts holding the motor to the kayak.

We decided to cut in an access hatch, Then permanently seal it up as we did not want any leaks and this hatch was not to be used again so this seemed the best idea.

The last thing we wanted was to start sinking out at sea.

Sealed Hatch


NOTE: I gave the job of sealing the hatch to Jack and didn’t take into account the rough surface of the yak when sealing the 3″ hatch in.

I wish I had done it now, But anyway it didn’t leak so the end goal was achieved even if it could have been considerably neater.


Once we had decided that a 3″ hatch was how we would get access inside, I set about designing a mounting frame that would be strong and light.

Making sure there were enough fixings attaching the mount to the to BGII, Ensuring as much weight was spread as evenly as possible.

See A few pictures of the mount itself below.


For custom steering, fuel line and tank install also custom throttle and mount.

Finished Mount


The entire mount is constructed from 316 stainless (including all fixings).

Using a series of pieces/lengths of 25mm x 25mm Angle.

1 piece/length of 40mm x 60mm Angle on the back and two pieces of 25mm x 3mm Flat Bar on the 45 degree angled supports.

25mm x 25mm Angle
25 x 3mm Flat Bar
40mm x 40mm Angle

There are 3 x M10, 316 Button Head Set Screws (bolts), On either side as seen on the top.

Also, 2 x M10 Button Head Set Screws in the 40mm x 40mm angle see picture below.

M10 Fixings

To start we cut the 40mm x 40mm Angle and Pre-drilled the 2 x M10 fixing holes as well.

We lined up the 40mm x 40mm Angle with the top of the BGII and drilled through the pre-drilled Angle into the kayak hull.

We then fitted this roughly with 2 x M10 bolts and Normal Nuts (as this would be coming on and off a few times).

Then cut down the 2 x lengths of 25mm x 25mm Angle needed for the two side supports and pre-drilled the 6 x M10 (3 in each) M10 fixing holes in these as well.

Next, we lined these up with the 40mm x 40mm Angle and stuck a few tiny tack welds on. Making sure the BGII was covered up with a couple of welding blankets. ALSO MAKING SURE WE DIDNT MELT ANY OF THE KAYAK!!!


Then we unbolted the 40mm x 40mm Angle from the rear, With the 25mm x 25mm Angle tack welded to it and welded these fully all around. Then cleaned up and de-burred any sharp edges.



Next re-attaching the mount so far to the BGII putting the two bolts in the rear again and nipping them up.

Next, we drilled through the 6 x M10 pre-drilled holes we made earlier into the kayak hull. Then we removed this again and de-burred all the holes in the hull and refitted the mount assemble again.

We put all the bolts’ in this time and “nipped” them all up.

Next cutting 2 x uprights and 2 x Cross members from 25mm x 25mm Angle.


Next, we had to decide what angle to set the motor at???

This was a massive gamble here…

As your motor needs to be at a set height in the water and a set angle to get the correct propulsion through the water. If these dimensions and angles are wrong the end result will be poor performance I.E. wasting fuel and slow speed through the water.

We had no idea at all how the kayak would sit in the water with this extra weight on the back or what angle we would need to set the motor at, To counteract this. So we made an educated guess between Myself, Jack, and my Old Man (another Engineer).

As you will see in the videos below, We got as close to “spot on” as I think you will get, Without building your kayak in a pond or lake.

Anyway, So once your happy you have the correct angle, Tack weld the two uprights on. Then the top Cross Member and lastly the lower Cross Member.

Motor Mount

Mounting Plate Material:

Remove the mounting assembly from the kayak and fully weld all the joints on the mount. De-burr and clean up the entire mount with a sanding disc in the 115m angle grinder. Once cooled use a buffing disc in the angle grinder and bring to a polished shiny finish.

Now it’s time to “decide” what material you want to make your “mount plate” from. We used some 25mm thick plastic I had “for a rainy day”. That was from a couple of commercial fish chopping boards I found ages ago.

You could use marine ply or Stainless, Aluminium, or whatever you choose. Marine ply would have looked better but I didn’t want to muck about varnishing things or replacing at a later date. The plastic we had was ideal as it will never rot and is water-resistant.

We didn’t use steel:

Because the Outboard motor mount “screws” needs to “bite or Grab”, The material your “mounting plate” is made from.

Using steel might result in the Outboard motor slipping around on the mounting plate when in the waves.

Once completed we used CT1 Sealant in between the mount and the kayak

Sealing all the holes up and giving maximum support.

Add Sealant:

Add some sealant to the Mount and stick Mount down. Align all holes and put the M10 bolts in.

Then put oversize repair washers and Nyloc M10 nuts on the inside of the hull.

Tighten everything up whilst trying to minimize the amount of CT1 going everywhere.

Once all fixings are nice and tight

Clean up the outside of the kayak and remove all CT1 from the kayak, The Mount, and yourself.

As it will be all over your hands, Up your arms and probably on your face.

Let CT1 dry and the job is finished.

Chuck on the motor and go for a spin…

See below a few videos of us using them in off the Cornish coast.

Don’t forget to check out ourGallery” “Kayak Builds and Mods” “YOUTUBE




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