cupless in stainless

[Billfo]

I have the opportunity to get a good deal on a prop same pitch & diameter as my alum
EXCEPT in stainless & without the cup.
In theory, how should this perform ? Would there be a noticeable difference ?
Thanks, Billfo

 

[hwsiii]

Re: cupless in stainless

Bill, it will depend mainly on the differences in blade area and blade geometry and how high your motor is mounted on your transom, but you can always get cup added to a prop.


H

 

[walleyehed]

Re: cupless in stainless

In general, an un-cupped prop of a given pitch will act close to a cupped prop of 2" less pitch- RPM wise.
An un-cupped prop tends to be used on stern-heavy boats and is likely an older design. As expected, the nose tends to drop at higher throttle settings as well. Been a long time since I've seen an un-cupped SS Prop.

 

[Billfo]

Re: cupless in stainless

Thanks... I will pass on this prop.

 

[Billfo]

Re: cupless in stainless

Ok I passed on that prop, but in return the guy asked me why & asked WHAT I was trying to accomplish. I told him I was trying to gain another 200-300 rpms. He told me use the same prop in stainless & just less 1/2" diameter.. That simple. (per him).. Any comments ?

In general, an un-cupped prop of a given pitch will act close to a cupped prop of 2" less pitch- RPM wise.
An un-cupped prop tends to be used on stern-heavy boats and is likely an older design. As expected, the nose tends to drop at higher throttle settings as well. Been a long time since I've seen an un-cupped SS Prop.

 

[Chris's CVX16]

Re: cupless in stainless

Wow that's quite a response from the seller.

It might be that simple but good luck finding a prop that is exactly the same on the other characteristics but 1/2" less diameter.

While it might be true dropping diameter will raise RPM's it also lowers the prop's drag and load on the motor. Also lowers the props thrust and acceleration.

I no longer own anything but stainless props. Keep looking. If the price is right try same diameter/pitch/rake/blade type in Stainless. That might be all you need.

 

[Billfo]

Re: cupless in stainless

This prop business is quite an art form.. Thanks for your experience !

Wow that's quite a response from the seller.

It might be that simple but good luck finding a prop that is exactly the same on the other characteristics but 1/2" less diameter.

While it might be true dropping diameter will raise RPM's it also lowers the prop's drag and load on the motor. Also lowers the props thrust and acceleration.

I no longer own anything but stainless props. Keep looking. If the price is right try same diameter/pitch/rake/blade type in Stainless. That might be all you need.

 

[Chris's CVX16]

Re: cupless in stainless

This prop business is quite an art form.. Thanks for your experience !

Oh ya. "Art" is a very good way of putting it.

What is real odd is you can have 2 identical props and get different results from them. It might not be significant enough to notice or it might be something you realize after a minute of use.