Prop Diameter Question

[rutcutter]

It is easy to find information on prop pitch but I have seen very little info on the effects of changing the diameter of the prop. So my question is this.
Is there a rule of thumb regarding the effect of diameter change on WOT RPM's like the rule of 100 to 200 RPM change per inch of pitch change? I understand that there are rather extreme limits on how much you can increase diameter but how much can you decrease it?
The real purpose here is that I am trying to increase the RPM's on my boat with minimal pitch change and I want to know if using a smaller diameter will accomplish this and what possible problems I could encounter along the way.

Thanks.

 

[Tail_Gunner]

Re: Prop Diameter Question

It is easy to find information on prop pitch but I have seen very little info on the effects of changing the diameter of the prop. So my question is this.
Is there a rule of thumb regarding the effect of diameter change on WOT RPM's like the rule of 100 to 200 RPM change per inch of pitch change? I understand that there are rather extreme limits on how much you can increase diameter but how much can you decrease it?
The real purpose here is that I am trying to increase the RPM's on my boat with minimal pitch change and I want to know if using a smaller diameter will accomplish this and what possible problems I could encounter along the way.

Thanks.[/QUOTe

Diameter has little if any effect on boat props....You drive accepts a 5" (approx) prop barrell...Now if you put a 4 1/2 or 4" barrell on it your going to create a large disturbance in water flow which in turn will lower performance...