From 16X11 2 blades to 3: What size?

[Philip_Oceanis 361]

I currently have a perfectly sized fixed 2-blade propeller in my boat (Beneteau 361) that loads the engine to 3500rpm according to the manufacturer (Volvo Penta). The size of the prop is 16X11 (blade area approx. 34%).
What do you think could be the ideal size for a 3-blade fixed propeller (blade area approx. 52%)? 16X11, 16X10, 15X11 something else?
I would really really like to have (at least) the same speed at 2400-2500 cruising rpm as the current 2-blades unit.
Thanks

PS: Current propeller is the K11 model made from Radice (http://www.elicheradice.com/) and proposed 3-blade is the E13 model again made from Radice.

 

[Bill1565]

Why mess with perfection? Spend the money on something that will improve your boat.

 

[Philip_Oceanis 361]

Why mess with perfection? Spend the money on something that will improve your boat.

The "perfect" only refers to the tried and perfect size as to base the calculations for a 3-blader.
Any suggestions of size on selecting a 3-blader?
Thanks

 

[Steve Dion]

Suggest that you have a prop shop size the "Perfect" prop.

The normal rule of thumb would be to reduce the pitch by 1 deg when adding a blade or decreasing the diameter by 1 inch when adding a blade.

If you have any issues with prop walk, decreasing the diameter may be better.

I would not purchase a new prop without the advise of a reputable shop. They have computer programs which can calculate the size.