Using a prop from a bow thruster

Hi!

I’ve had my eyes on these bow prop propellers for a while now. I had an accident with my three blade and decided to give it a try.

There are multiple brands and props out there they are all made to be used in a duct. I managed to find one that’s 140mm in dia.

The prop uses a shear pin to keep it in place and normally a bolt/nut to keep it from falling of the shaft.

The one I choose came with a 11,5-ish mm bore so I decided to adapt it to my 10mm shaft.

First I drilled the bore in the prop to 12mm and the got a 12mm stainless pipe with 1mm walls. I cut the pipe to the right length and used an hydraulic press to fix the pipe in the prop.

I then drilled a hole in the shaft for the shear pin and also made a cut for the clip that hold the prop in place.

Hopefully I will get it in the water for a trial soon.

The hub on the prop is a bit bigger than the hiorth original and I might do a 3D print add on to the torpedo to get a smooth overlap between torpedo and prop.

This is the prop I got:

5 Likes

Nice catch ! Looks to have an efficiency between the Aliexpress 10USD 7 1/4" prop and the Flying Rodeo one.
Do you have an idea of the optimum RPM ?
P175 if in mm does it mean 6.9" pitch ?
Looking forward to you first water trial.

No numbers. Thin blades, feels strong.
I think the bow thruster is a 2,2kw machine.

Very interesting prop! I see they are very well priced at around £22 in the UK. Might have to try one…

There is a 180mm that looks like a sub prop to :slight_smile:

You talking about this one: https://www.sparesmarine.co.uk/webshop/bow-thrusters/all-quick-bow-thruster-spares/propellers/quick-fvsgel125000a00-osp-kit-propeller-d125/

Think its a 125mm one.

This is also pretty interesting… https://www.getaprop.com/lewmar-propeller-140tt

I’m sure @Dynamik will have some strongly held opinions about this! :rofl:

Let us know how it works. :sunglasses::call_me_hand::surfing_man::beers:

1 Like

Sure does! The pitch look higher. By the name one would think it’s 140mm dia.

Mounted and ready. Hopefully I can run a test next weekend.

4 Likes

Max 29,5kmh at full throttle. No vibrations.

Amp meter broke down last run so I don’t have a amp draw.

8 Likes

Speed wise how does that compare to your other props?

It’s 5-10kmh slower than the orange one that got eaten by seaweed. But it comes with better balance and less vibrations.

I think it’s a good prop, blades are thin, sharp and very firm.

I think I got the pitch measured to 5.8”. If that’s correct I would love a 8” version.

Hi Riwi
May be this propeller would do better in a slightly narrower duct. As far as I can see in your pics there is a gap between the blade tips and the inner surface of your duct. As you will know, at the acting propeller every blade has a pressure side and a suction side. These pressure differences try to short cut over the wide blade tips. Therefore it isnormally a design goal to keep the gap between blade tips and duct as narrow as possible. I don’t know, if the present gap is needed because of any deformation of prop or duct to aviod kontact. Otherwise it could be worth a try to print a new duct.

Have you tried without duct, the theoretical max efficiency limit of this prop ?

Look who’s here, the BTQ 140 blade! I know something about that prop, it’s been my daily nightmare for some time on boat thrusters, untill I realized that was “softening” hence bending after some time in water (it’s injection molded out of nylon, hygroscopic, with fiberglass) and we moved up to 50% fiberglass, check if it has a small circle with 50 written inside.
P175 I don’t think refers to pitch, but later I’ll ask to the guy who designed it.
This one push less than 35kgf at 4500rpm I remember…12V motor loaded at almost 3kw max peak. For speed I don’t think its really efficient but for sure it’s very well built.
There’s also a 125mm model, better design, 5blades…traction is made differently (splined shaft). It pushes shy 30kgf at 5k rpm, don’t remember current/power though.
In UK there’s Quick UK in South Hampton, good guys, National importer.

1 Like

Hey!

I love the fact that you worked with it, it’s high quality and not a bad prop for the price. The shear pin approach is nice to. Much easier to change the prop if needed.

More tests to come.

I can confirm the pitch: 175mm.
Eventually, check the FVSGEL125000A00 - OSP KIT 125 PROPELLER, it has a more aggressive pitch, other than more “directional” as blade profile. Don’t remember the exact pitch but I’ll ask to my former colleagues.

Ate there any hub dimensions available?

Thanks!

Can you confirm that the shaft for the 140mm fits the 125?