Yes, these work extremely well and are used for engines with lots of pressure behind them. You must be sure they fit tight and you pack around the shaft and in the seal with marine grease. This is as good as it gets.
You mentioned these seals are used for water pumps and want to know if it will be enough.
Bottom line you/we are building a water pump…
- a shaft with propeller pushing water
- All shaft seals will let in some water, these seals do the best job that I have found. Remember, all boats have a bilge pump because water is nearly impossible to keep out no matter the seal.
You could do a double seal, one on the inside, pack it with marine grease then put another seal on the outside, but that will increase the motor current as seals do have some friction.
I have had my electric hydrofoil under water all day and night last night, Ill be opening it up to see if my paper towels are still dry later today as I redesigned some 3D parts the other day.
hope this helps?
It helps a lot! Thank you for shareing! Maybe you could start your own post about your build 
SURE @LukePL
Yes, Im about to start sharing my build on my website here and also on my youtube channel
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I have posted some information on propellers and ducted propellers if anyone wants more info: DIY Electric Hydrofoil 3D Printed Propellers and More… - http://www.diy-electric-hydrofoil.com/diy-electric-hydrofoil-3d-printed-propellers/
Ducted Propellers Should Be Used with DIY Electric Hydrofoil - http://www.diy-electric-hydrofoil.com/ducted-propellers-used-diy-electric-hydrofoil/
“Ducted Propellers I believe should be used for a couple of reasons. The main one to me is actually safety. I keep seeing people build and test boards with no protection from the propeller, and its just a matter of time before someone loses a lot of blood or worse…”
Yes because a duct is VERY likely to introduce a tremendous amount of drag, a properly designed duct could help you but it is so hard to get right that omitting a duct in the first tests will help you verify the motor / reduction / propeller first (which is challenging enough by itself ).
(battery voltag - motor kv and current - reduction - propeller pitch / surface area) really need to be matched, simply purchasing / printing a propeller wil result in burned motors, broken gearboxes and very limited propulsion power.
The duct you show in your pictures seem to have no (naca like) profile at all, is it simply rectangular when you look at its cross section? If so, this duct will add significant drag instead of efficiency.
I am unable to find the xjet followup video where he actually attempts to prove his theory, do you know where I can find that video? I think its highly unlikely a duct will improve efficiency. A duct might improve trust with the drawback that you have to put in way more power (thus lower efficiency). Just look at 95% of all marine propeller and surroundings, no ducts are used. If dutcs were to improve efficiency they would have been widely adopted already.
The rake determines the angle of the board? I highly doubt that. The angle of the board is more likely to be a balance between total weight - foil design / profile - speed.
Have you designed any propeller / foil in the past? On what information is you story based?
What battery voltage / motor kv / gear box ratio and prop pitch did you chose?
If you read the articles I posted you will see the video and details. All this info is from reputable propeller websites, and educationals videos (video posted in article)
As stated in the article Ducts are great for lower speeds and high thrust. You wont see them on speedboats, but you see them where the prop needs to be protected or when users need to be protected. Ducted props are everywhere. You simply do not understand the power of a foil wing which a ducted propeller has and this is explained in laymen terms in the video bottom of page http://www.diy-electric-hydrofoil.com/ducted-propellers-used-diy-electric-hydrofoil/
High rake forces more of the waters force directly out the back of propeller, VS a low rake which forces much more of the energy out the sides of prop, reducing the amount of straight back thrust. Rake explained here: http://www.propellerworld.co.uk/Prop_Basics,_how_propellers_wor.html and also here: http://bblades.com/props-101/
Of course you need to match motor, KV/volts etc… with prop, thats a given… Those who done, blow ESC’s and motors are you know
Good questions, thanks.
I know xjet, i have seen his video, he claims things with his limited understanding. He talks a lot, really a lot, he realises however almost nothing. I also couldn’t find his video where he proves it. And with his example as well, if ducts were to introduce efficiency, why aren’t they used with quad copters / dji phantoms?
Like I said, the only useful feature of the duct is protection. Further the duct will likely introduce only drag. Please elaborate on everywhere, I cant seem to find examples of a widely adopted use of the duct.
The angle of attack, foil profile, weight it has to carry and speed determines the board angle. Rake will have very little / almost no influence.
Again, have you ever designed a prop? Have you ever designed a foiling object? All your explanation seem to be based on stuff you read on some website. Please be reserved / hold back a little with your claims and telling on how something works until you actually realised / tested the theory and have a thorough understanding of the complete system.
What battery voltage / motor kv / gear box ratio and prop pitch did you chose?
The data is everywhere on the web talking about ducted propellers (kort nozzles) like here on wikipedia: https://en.wikipedia.org/wiki/Ducted_propeller also the video I provided explains all this…
Go to virtually all propeller websites, or brand name sites like Mercury etc… they all talk about higher rakes working better in aerated waters, helping keep bow lifted etc…
Of course I get my information from the web through lots of research.
Ducts are used on some drones and helicopters but they those machines fly somewhat sideways to the prop/duct, it’s not ideal for ducted propeller which makes logical sense if you think about it.
I think it’s just best we agree to disagree, thanks for your feedback and hope you watch read about these things to learn more.
cheers!
LukePL how are things going with your build? did you get the shaft seal and test it out yet?
Also, I posted an update on my blog about building an affordable DIY eFoil
For now I’m trying to figure out what size of jet drive I would need, what motor and barttery. E-foil looks super fun but i’m worried because of water plants in lake where I’ll use the board. Long roadster ahead 
As for the sealings I was not able to find them localy but please take a look at those http://www.e-simmering.pl/pl/p/Uszczelniacz-8x22x77%2C5-CORTECO-12011511B/1366 … and this https://m.banggood.com/8mmx10mm-Aluminum-Flexible-Spider-Shaft-Coupling-OD25mm-x-L30mm-CNC-Stepper-Motor-Coupler-Connector-p-995810.html?rmmds=detail-bottom-alsolike
I’m looking for some cheap parts as this whole thing is an experiment. I learn how to design jet propeller and I’ll try to design jet drive for 3D print. I have a 3D printer so I’m able to test some different solutions 
Sounds good Luke. Couple thoughts… I used these couplers: https://www.amazon.ca/gp/product/B01D61999W/ref=ya_st_dp_summary?ie=UTF8&psc=1
The shaft seal, the company I used ships anywhere: https://www.bearingscanada.com/ProductDetails.asp?ProductCode=TC8x23x5&CartID=1
Keep in mind, depending on what you consider cheap, this may not be a cheap experiment. You are technically designing and building a watertight remote control jet drive (motor assembly, propeller assembly, battery and ESC assembly, and need to create a waterproof remote control)
Just basic part cost not including couple dozen little things that add up really fast are: Motor $150-$250 ESC $125-$225 Transmitter & receiver $35-$75 3D printer and or printer filament $99- $150 (Nylon is not cheap but can handle the heat and stress) Reduction gear $124-$375 Water box for battery and esc $50 Batteries $200 (dont have a charger and leads? $150-$200) Then, o-rings, seals, couplers, aluminum, wiring, connectors, SS bolts and nuts, conductive paste, propellers, shaft, etc…) I ended up having to buying a bunch of tools to complete the build as well.
As you can see, buying just the basic parts alone will bring you $1000 in a blink of an eye.
I have been working with manufacturers of the main parts I have used, and with a bulk order I can save 45%-85% on all the expensive parts, and have them arrive with all the custom connections ready to just bolt it together, plug the parts in, and start riding with the DIY Electric Hydrofoil setup I’m working on meaning at no extra cost to you for all the parts you could get the complete kit of all parts ready to be assembled. Just a thought as my goal is to make this simple for us all…
Side note, no matter what setup you use if there are a lot of weeds hitting your prop or getting sucked into your jet duct, it WILL be an issue
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Oh yes I don’t try to tell it’s going to be cheap I’m just trying to keep cost low as possible. Looking at your part list I wonder do I need reduction? I think that jet drive needs much more rpm than efoil? Maybe you can advice in that regard.
What is a difference between rigid and elastic coupling?
As for 3D printer I have Zortrax so materials are limited. Recently they came out with PC-ABS. Its a mix of ABS with POLICARBONYTE so I think it will do the job for testing.
Those water plant are about 0,5m under water surface in areas where they are (not all lake) so that’s why I think jet will be ok
Thanks for the tips and ca’t wait to see some videos of your work and maybe see some data regarding motor rpms (without reduction gears) amps and other stuff 
@thetechtrader what gear reduction are you using?
@LukePL I’ve been trying to go without a reduction. Working on some props for higher RPM…
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Nice looking setup! Ya I have a 5:1, and 3:1, and a smaller prop setup for direct drive as well, as thats the most simple, compact, and cost efficient way to build it, just need the thrust, which is an issue with smaller prop, but I believe its doable…
Sorry for the delay getting back to you, I have a no-name reduction gears for testing RPM’s as the brand name units are $300 - $400 USD each, not cheap when you just wanna test as setup.
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I just posted some info on another setup allowing the Efoil drive to quick connect onto any surfboard or SUP, and why I prefer under-mount VS jet impeller for an electric surfboard.
Check it out: [DIY eSurfboard] (http://www.diy-electric-hydrofoil.com/diy-esurfboard-build-progress-benefits-mount-vs-jet-drive/) - http://www.diy-electric-hydrofoil.com/diy-esurfboard-build-progress-benefits-mount-vs-jet-drive/
Also, Sunday I plan to post my first video of my build
That’s so cool you are on this forum! I binge watched your series. I decided to sell a few of my land boards to make room for a foil before I leave Hawaii.
I like it. Looks very fun