Electric motors for boats are becoming popular.

I imagine one of the difficulties is keeping the electric motor sealed on the rotating shaft so water can't get in.

I propose that the stator of the motor is sealed in a dry area, and the rotor is outside in the water.

It is important to minimize the separation between the stator and rotor. The stator is keep in a strong thin plastic that radially surrounds the rotor.

My favorite type of electric motor is switched reluctance motor, which would be perfect for this application since the rotor is so simple: just a chunk of metal with arms radiating for the centre. The metal would be a rust-proof such as stainless steel. The rotor would be removable so could be easily cleaned.

Anyway, the idea is that the motor wouldn't need waterproof sealing (between moving parts) so could be cheaper, more efficient, etc.
-- xaviergisz, Jul 12 2025

ROV thruster idea https://www.youtube...watch?v=zdjgxerAekQ
[bhumphrys, Jul 12 2025]

[+] If the stator was in a submerged keel cowling and the propellor used a fluid or air bearing to minimize friction at the perimeter, this could spin like a waterjet with no through-hull fittings and very minimum drag. It still needs to push or pull on something to move the boat, though.
-- minoradjustments, Jul 12 2025


Nice! like the one on the link?
-- bhumphrys, Jul 12 2025


Very cool.
-- 2 fries shy of a happy meal, Jul 13 2025


The ROV thruster in the link is conceptually similar, but executed differently. It is a full motor sealed in the housing which is magnetically coupled to the propellor. There are a few problems with the design: no bearings (so lots of friction), and no axial support/bearing (which would limit the thrust).
-- xaviergisz, Jul 14 2025


//It still needs to push or pull on something to move the boat, though.//

Wheels or bearings in the front and back, shouldn't be a problem. [+]
-- doctorremulac3, Jul 14 2025



random, halfbakery