Keyway Shaft Practicality?

Hi Folks -

Relatively new and doing my absolute best to read, read, read… lots to digest.

My use case is not specific to an e-foil but rather a larger hull (small boat (kayak), ~13ft, 120lb hull) which I plan to use two hydrofoils on (center and rear) to provide a more economical and high speed method of point A to point B. There is a similar commercial product for sailboats of roughly the same profile called Foilsz, so I believe it’s a feasible goal.

I am looking at an MTI85165 which I believe will provide the required power / speed for liftoff relative to the increased drag and weight of the hull versus the more commonly used 6516X.

I’ve run into many motors with a “keyway” shaft, and that’s the only version the 85165 (no sensor) that Maytech has in stock. However, I haven’t been able to find any useful information about the practicality of a keyway shaft or how to mate it with a propeller. In fact, what I have been able to find on this forum seems to indicate “always screw”. Is there a real world way to mate a keyway shaft with any commercially available propellers?

Maytech doesn’t seem to have any interest in building more screw shafts of the 85165 for less than a 10 MOQ, because “customer has feedback before that wants keyways shaft”… so what’s the point of a keyway shaft?

Cheers !

If you 3D print your prop, you can easily use a key (as long as the material is strong enough). You could also dril a 4mm hole into the shaft with a carbide drillbit. Design and 3D print a drill Jig, you can add a small bearing with ID 4mm to guide the drill bit.


Thanks for the ideas. Sounds like a keyway shaft can be made workable with some effort but isnt ideal.

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Hi and welcome to the forum !

I believe you migh be interested in some readings here : Share your builds here! - #16 by Juless

Long story short, I wouldn’t use those motors for your build. I’d rather go for the same solution used on the solar boat you can see following the link above, and instead of going with a “push up” configuration, I would make sure to go with a “pull up” as they did :wink:

Thank you! I’ve now gone down a whole other rabbit hole of the difference between push and pull props.

Can you help clarify why you think the 85165 motor selection isn’t ideal? Reading through the solar boat details it seems that they only need ~3kW to get lift on their platform with 6.5kW for top speed but their motor is rated at 17kW. Seems like it might be overkill? Surely something I’m not grasping :slight_smile: