Interesting, I moved away from active pump and downward pointing tube since the pumps are shitty and start to leak by themselves. Now I have a mast clamp with opening at the tip for passive watercooling. I do not use a tube, but rather have the whole mast cavity as channel. On top it is sealed and i have added some alumina pipe to connect a silicon tube. you can see it here:
Actually, I do not need much of velocity to keep the water running. When not flying the water level is already quite high in the cooling circuit and just a bit of pressure will start it flowing. The outtake is at the end of the board, so it is easy to see if it is still working while foiling. So far there was never something stuck.
For the pump however I had blockage cuz if I were to close to the ground (eg putting the board into the water) it could happen that it will suck up little rocks from shallow beach area.
@tinp123 : I would just raise motor current by 10amp settings. Start from e.g. 150. For me it is quite the case that I have a really hard time to get flying with 150amp whereas 160amp will jump me out of the water. So try to approach the issue like this instead of pushing too fast too high currents
Was this full throttle?