2-blades 16X11 vs 3-blades 16X10

[cmedsailor]

Some days ago I begun a thread being concerned how much more motoring ability would have a fixed 3 blade propeller in comparison to my current 2 blade. I got very good answers from lot of people and especially from “boatmike”.
Since I have now found out from the factory that my original 2-blade prop size is 16X11 and the only alternative I would choose would be 3-blade 16X10 (recommended by the factory) could anyone make a comparison (theoretical of course) of these two propellers?
Thank you again for your great help.

 

[boatmike]

In simple terms the 3 blade 16x10 will give you less slip due to its greater area. However 1" difference in pitch is 10% less so you will theoretically(disregarding the slip) require 10% more RPM to reach the same boat speed. Assuming you are running at 2500RPM now that will mean 2750RPM to break even. However the 3 blade will have less slip even in calm water so lets say that would be more like 2650 -2700RPM in reality.
In adverse conditions however the slip on the two blader will knock the speed back much more than the 3 blader so 2700RPM will possibly give much nearer hull speed with the 3blader than with the 2 blader.
Disregarding sailing performance, it sounds like a good choice and your original problem of speed reduction in adverse conditions should be greatly improved. In fact the finer pitch and higher RPM will feel like you have changed down a gear in your car and you will climb hills without putting your foot on the floor.
Hope this is clear (calculations only meant to be approximate to illustrate)

 

[cmedsailor]

THANK YOU

 

[boatmike]

You are very welcome...