@pacificmeister: Yes, because the higher pressure comes from the water side. But I think it only get relevant if you have a higher pressure difference like in a combustion motor.
The more important fact is too keep the shaft spinning completely centric. I struggle with the same problem although I have a second bearing. The non centric rotation t is coming from the bad quality of the coupler.
Vibrations also might be more significant due to unbalanced prop ( which is 3d printed). So prop balancing is important to reduce vibrations as much as possible:
Cheap couplers, chafts, and unbalanced props will definitely cause a wobble which leads to shaft seal leakage. If you can use a flex coupler of some kind between motor and prop it can help reduce this. The longer your shaft the more the wobble in amplified and stratch the shaft seal/leak.
@pacificmeister Hey Merten, hope you are having a nice weekend.
I was just going through your parts list and see you have bought the same cooling pump as me.
just giving you the heads up that the pump you have isnt āself primingā . I made this mistake also.
unless you are going to mount it at the bottom of the mast it will be a nightmare to pre prime it for
water circulation.
Cheers, David
Hey David, thanks for the info, good to know. It is still in the box, not doing any water cooling yet. I saw people discussing that we might get away without pumps if the intake is positioned right. And with pump, wouldnāt the travel speed in a similar way help to prime it eventually?
I dont know, the travel speed might work but then again it might not! wouldnt like to take the risk. I did some static testing with a 1 meter length of pipe into water and it didnt work at all.
I think we may need to put a water cooling nozzle in the duct to get water pressure from the prop thust
Yup, thats what we did, works very well.
I though of this but wiped it off the whiteboard because I didnāt think the prop wash would be enough to push water up the mast and around the esc/batteries.
Are you getting good pressure ?
Cheers, DavidC
Yes, great pressure and we had 10foot water line, it actually surprised me. It will be better when we have our electronics mounted inside the middle of our board, reduce 5ā of hose will definitely help in reducing back pressure.
Wow Iām very impressed, could you post a photo of your water cooling setup to help me understand how you ha e ran your tubes ha.
Cheers
Hi, have anyone of u made the experience that the 3Prop is a tinny little bit to big for the Duct?
It fits but it doesent run 100% free.
@pacificmeister
to you made the thread on the shaft for the prop mounting by yourself?
Or do you bought this part finished?
greets from Austria
@overdrive. I assume itās printer tolerances. My little Qidi x-one is a bit misaligned, so the prop and duck are slightly oval - therefore not spinning free and I had to file the prop down. I printed the exact same on Donās Raise3D printer and it fits and spins perfectly.
Regarding the shaft thread, yes I cut it. Bought this kit to have the M8 tapping tool:
https://www.amazon.com/dp/B01MRQNSTL/ref=cm_sw_r_cp_apip_jA8qmjrN6RRWf
Ok, i think i will scale down the prop 1% and then i will see.
Ok thank you for the link to the tools. I think i can borrow this stuff from a friend.
In former days it had such tools in my service car 
Also the connection between duct and sealmount stuck at the last winding of the thread.
At the end i will print it with 100% infill but for now i have to find away the every part fit together.
I didnt get any photos and since then I have sold all my parts for that particular reduction gear drive as we are direct drive mini prop and also a jet drive version. But we used 1/8" copper tubing for the pickup behind the prop, and then clear 1/8" up the mast.
I should mention, we are also using a smaller prop than the reduction gear drive guys so our water pressure is much higher behind our prop than say a 120-170mm prop which pushes the same kg thrust of water spread out over a larger/wider area.
Yeah I get you! Iām in favour of the direct drive! Would love to know if jefoiler and lift are direct drive or geared
Hi Guys,
I am so grateful to pacificmeister and to all the other contributors for sharing your expertise and experience in this forum. I have learned so much.
A thought about the motor/prop unit:
is there there enough room for a quick disconnect for the wires in the nose cone?this would allow the easy removal of the motor and prop portion from the foil without having to disassemble the entire rig.
Aside from easy removal for repair, it would also allow swaping of the moter/prop portion between builders to see differences in performance and compare builds.
