One decision that will help determine the length of your tube is whether you want to be able to disconnect the motor. Some have elected to permanently crimp the wires to the motor; thus the motor cannot detach. Crimping instead of solder means there are no soldered connections to melt and detach if there is high heat. And you can make your tube shorter since the motor is not sliding out of it. On my build I chose to make the motor wires long enough to pull the motor all the way out the rear of the tube so I can disconnect it (using the existing SSS motor connectors). This required a much longer tube to store the longer wires. Time will tell if my decision is a good one – or not. I do like being able to inspect or swap out the motor if necessary.
Not good 
I thought I would get good pressure there, but it didnt work. Im going to use a pump instead.
Place the tube in the front section of the mast clamp. That’s how lift have done it and I have also had success with it like that. The only drawback is that after riding the ESC does not have some water flow to cool quickly.
On my build I only kick in the pump if the ESC goes above 40 degrees. But the natural flow seemed to keep it off anyway.
thank you for your advice, the fact of having to pierce the forehead mastclamp does it rosè it does not weaken the latter …? this is what I planned to do as an installation with a self-priming pump:
Pump KAOMER https://fr.aliexpress.com/item/Kamoer-KLP05-6-Vacuum-pump-Water-and-Gas/32828251174.html?spm=a2g0s.13010208.99999999.312.7f053c00u5XGiP
in red this is this piece:
http://www.racing-power-boat-rc.com/Rc-offshore/refroidissement-eau/raccord-durite-m-5mm-cuivre/
Yes and the bottom shape like this
http://www.racing-power-boat-rc.com/Rc-offshore/refroidissement-eau/prise-deau-simple-coque-offshore-rc-piece-modelisme/
More size here
Nice ! Where did you purchase the magnet / switch please ? Any link ?
Thank you
Hello in this shop :
https://www.ruedelamer.com/ignition-cut-off-device-complying-with-regulations-560bd4e565b9b.html
Number look good 
…
Yes, it is a two-part aluminium shaft. But I had it remanufactured in one part… I don’t know if it’s good… and to prevent it from rotating in vacuum I kept the key of the NEUGART gearbox