Pacificmeister Build Info and CAD Sources

We fill the entire compartment with it :slight_smile: Act as an extra seal if the shaft seals break as well.


Hi Fabien
I chose a 12v pump to cool my ESC, it must connect to the receiver powered by the output of the nozzle in 5.5v
should it feed différently ?

If it’s 12V, use a small DC-DC booster step up from UBec to pump. I bought a 1€ module and it works just fine. You can set even just 9 or 10V for less pressure out of the pump

Thank you for your help
I found to bangood an ajustable output voltage ubec to 12v and input 2-6 s power battery.
But my receiver remote support only 5,5 v i think
Can you send me schématic or picture to connexions
The Ubec is a device that reduces the battery voltage down to a value suitable for our RC receiver module, usually something from 5 to 6.5V (check your own).
So you will have battery>UBec>receiver, Ubec should be in parallel to ESC.
Then, if you need to power other electronics or a pump (like in your case), you should get a double output Ubec (expensive, not easy to source, expecially able to cope with 12S battery) or just parallel a cheap and simple device like Step Up boosters, they cost a fraction of an Ubec, you need to solder 2 wires on input and 2 on output, place them inside a piece of heatshrink or tape them (to insulate components), and that’s it. The video shows how to set the desired output Voltage, should be done by applying the same voltage you have on input (5.5V in your case).
Mine is inside black heatshrink tube so it make no sense to take a photo…
The same device, called “Buck Converter” or DC-DC step down, is used to reduce voltage with very high efficency.
You can’t squeeze lots of power out of those step up or step down, anyway. But to run a stupid membrane pump (less than 0.5A at 12V) you won’t have any problem.
LAst thing to keep in mind: switching converters are all about frequency, so they might cause disturbs, keep them not in contact with RC receiver and use a ferritis round core on the signal wire (like Pacificmeister and others do, just wrap the cable around the ferritis ring. - you can souce that on Hobby King or on the internet, very cheap)

@pacificmeister Hi, could you indicate which is the good duct ? Is it this 1: or this 2/ ?

Could we assemble these 2 ducts with the seamount ?Are the threats the same ?

The way is long !!!


Hi Mauro
Thank you for’your Help
I would buy and test it

Hi @cristophe, #1 works but has lot of drag at high speed. I did create #2 with a lower drag NACA0012 profile, but think I made the struts too thin. Haven’t modified and tested it yet. Both should fit the same sealmount yes. Only the duck ring diameter is different so adjust the prop if you try #2. Good luck and keep us posted.

Has anybody replied to @Ant about using a water jet turbine with much higher rpm and save the gearbox?

I was reading in different topics on this forum about kill switches / cutting power-disconnecting batteries (and getting zapped).
While the Hall switch looks a simple solution to stop the motor, I was thinking the following solution for a switch for disconnecting the batteries
(seems the huge current is an issue):
I ordered this high current fuse (credits to someone else on this forum / cannot find it back immediately); I did however order
the following rubber waterproof covers which I will glue into the cover of the battery box allowing me to use the fuse as a switch to
cut off the power. Maybe a simple idea to combine a switch and a fuse.


I had a similar idea but someone mentioned that these “high current” circuit breakers actually cannot handle the current they are rated for, due to the way they are designed. There is some youtube videos of them failing.

I still haven’t tested mine yet. There are lots of people who have mentioned them on there parts list so I assume some are using them. Would be good to get feedback from anyone whether they are using this type of ‘waterproof’ circuit breaker / fuse successfully?

I am using a fuse like this in my battery box. Just for over current protection, not as a switch. So far it didn’t pop on me. I assume it won’t last very long if you use it as switch and close it without pre-charging the esc capacitors.

Thanks, indeed. The waterproof cover would allow me at least to do an emergency disconnect-of-battery without the need to touch anything with wet hands. Closing this fuse is something I could do only after disconnecting the (XT90) connectors on the batteries, e.g. when safely ashore. So not really to be used as a rocker switch but rather as an emergency OFF. Btw, the waterproof cover would not allow me to close the fuse, only to push the button (which I hope is the one to open the fuse - I did not receive it yet)

You precharge the capacitors with a 500 ohm 5-10 watt resistor in parallel with the disconnect switch but with a separate disconnect.

hi, my water pump froze last week here in ireland, i had to rebuild the pump and change a few parts including the ceramic seal, the spring and central seal are on the water side of the pump, probably to keep lubrication between the ceramic face, it was interesting to see, its kind of changed my design of the final drive stage before the prop,
do you think it makes any difference?
having this side of the seal inside would make things a little easier to design


Hi @keith75, I assume it uses a mechanical face seal? That’s what I got first and planned on using before I learned about the double lip seals most of us use now. Lip seals are simple to install but face seals seem to be more durable, less friction and better sealing. Am not a seal expert but I heard face seals work mostly well with clean liquids and not with abrasive liquids which can damage the hard sealing surfaces. We have a chance for sand, mud or other fine debris in the water and it might impact seal life.


We use a lot of face seals in the oil industry. And drilling mud is a nasty thing some more than others, it can contain some solids and sometimes be very abrasive.
However, for our uses, lip seal are much easier to put in place.
Face seals needs to be spring loaded, have an oring on the shaft to seal with the rotating part and another one to seal between the housing and the stationary part. Also, they work if the housing is filled with oil and is pressure compensated. That might just be way to high-tech for us :slight_smile:


yea, true, good point, there is a risk of gritty dirt that would destroy the ceramic seal, i bought one 16mm internal dimension, but a low friction option sounds ideal, ill think about it, maybe the seal to be spring side out, with a fine stainless gauze with an o’ring on the prop shaft in front to keep out grit,

The vanes supporting the duct look to be twisted in the wrong direction. They appear to rotate the water in the same direction the prop is spinning. If you think about the limiting case (water spinning at the same rate as the prop) you would get no thrust at all. If the vanes were twisted in the other direction, they would straighten the flow of water exiting the duct, and may give better thrust at higher board speeds (because of the prop’s fixed angle of attack).

If I am wrong about this, please let me know why.

I’ve been studying your Fusion 360 designs & I have a question about what provides the counter torsion against the rotation of the the engine + gear box mount ?

As the engine is basically flush against the aluminium pipe (+ heat paste) and the other end of the tube has the 2 O rings on the seal mount, does this mean that friction & the 3 wire mounts take the rotational force at the front?

I wondered whether there would be 2 or 4 of bolts running through the rear mast clamp into the front of the motor.

Or am I missing something else?