I have made this propulsion system because I was curious to see if I like Jetsurf, short answer I don’t 
The system uses a 56154 280kv sss motor, paired with a 110mm duct propeller, the motor got some waterproofing updates: stator coating, ceramic bearings, and titanium hardware.
Che casing is 3d printed in sls nylon pa12
This unit was over 1k€ to make, and have less than 1h of use.
The system is very power hungry, at 40km/h I was drowning 7kw in a 12s configuration (motor can accept 20s, raccomanded will be 14s)
It’s using a standard efoil must, so you swap between systems
The small wing is for make some jumping.
You can use this system for towing as well
The system in action:
Photo:
Looking for 450€+shipping