alum to ss

[howlnmad]

This is just a general question, I'm not looking for a specific prop dia. or pitch. I read somewhere that if you change from alum to ss you have to change pitch. Can anyone tel me if this is true? And if so, why?

 

[Triton II]

Re: alum to ss

This is just a general question, I'm not looking for a specific prop dia. or pitch. I read somewhere that if you change from alum to ss you have to change pitch. Can anyone tel me if this is true? And if so, why?

Due to the inherent extra strength of SS compared to alloy, SS blades are generally slimmer and more hydrodynamically efficient i.e they are slightly better at converting engine power into thrust. So it's my understanding that for any given engine you need to fit a lower pitch SS prop in comparison to alloy to achieve the ideal level of performance.

An example: with my little Quintrex cuddy fitted with a FT60 Yam I went from a 13.5x15 pitch alloy to a 13.5x14 SS and got very similar (probably a bit better but immeasurable in the real world) holeshot with identical top speed, WOT rpm and fuel consumption figures. So in my case at least, a 7% reduction in pitch gave the same performance when swapping from alloy to SS. Others here can (and probably already have if you wish to try a search) give you a more detailed explanation. Good luck,

TII

 

[howlnmad]

Re: alum to ss

Triton,

Thank you very much. That makes sense to me.

 

[radarbugs]

Re: alum to ss

Just a newbie saying hello. I'm glad i fouind ya.
Radar

 

[jgoeden]

Re: alum to ss

The guy at a local boat store said that that alum props are "weaker" so they bend under load while a SS don't bend at all. I have a 19P on my boat and he said I need a 17P SS prop.

I can't confirm the accuracy of his knowledge but it makes sense.