Hi there,
This is Bogdan from Romania.
I'm a mechanical engineer - specialized in the industrial robotic field, 3D designer and modeler (from time to time and some projects I could make the functional prototype too).
I'm doing product design, industrial design, reverse engineering, ideation, etc.
I have over 15 years of experience working on various systems/devices across multiple industries, from concept to launch.
1 - in the first place, it looks like you chose a stern tube system, which is ok, but it also had higher friction for sealing the transmission shaft
2 - the entire assembly (and consequently the parts selection) needs to go one way or the other - it looks you have the given thrust, so will be necessary to start from there and chose the right propellers, the motors, and the battery...
3 - we could also discuss about designing the support designing for all the components, based on the hull model you have
i guess you already have the throttle and the controller for the motor(s) - it will be only one controller for all the motors (which will be connected in parallel in order to avoid differentiation)
we could discuss all the details here...
Regards
Bogdan